Biophysical

FATTY ACID BINDING PROTEIN(FABP)

Fatty acid binding protein (FABP) may be significantly elevated in an acute heart attack. It is a newly introduced plasma marker of acute myocardial infarction (AMI), with some advantages over myoglobin and troponin-I. The normal FABP level is approximately 1.5 ng/ml and increases to 20 ng/ml or greater following AMI. As with myoglobin, elevated plasma concentrations are seen within 2 hours after AMI and generally return to normal within 18 to 24 hours. Because the concentration of FABP in skeletal muscle is 20 times lower than in cardiac tissue, however, FABP is more cardiac-specific than myoglobin. FABP also appears to be a useful plasma marker for the estimation of infarct size.

FERRITIN

Ferritin is a protein that stores iron in blood. Its levels may be useful in the evaluation of anemia and may also be elevated in inflammation or liver disease. Ferritin is found in serum in low concentrations that are directly proportional to the body’s total iron stores. Serum ferritin levels are very helpful in the evaluation of iron deficiency anemia, anemia of chronic infection, thalassemia, and hemochromatosis. However, ferritin levels can be nonspecifically elevated in patients with inflammation or liver disease, regardless of iron stores, due to hepatocellular leakage of ferritin from damaged cells.

FIBRINOGEN

Fibrinogen is a protein that is transformed into fibrin, which is an important protein in the coagulation of the blood. Abnormal levels of fibrinogen may be related to bleeding or clotting disorders. Cleavage of soluble fibrinogen by thrombin to form fibrin is the final common reaction of the coagulation cascade. Low levels of fibrinogen are seen in association with excessive fibrinogen use (as in disseminated intravascular coagulation), primary fibrinolysis, and liver disease. A high fibrinogen level is a risk factor for thrombosis and a strong predictor of cardiovascular risk and stroke, particularly in young adults. Low-dose heparin and ACE inhibitors reduce fibrinogen and the risk of cardiovascular events.

FIBROBLAST GROWTH FACTOR-BASIC FORM(FGF-BASIC)

Fibroblast growth factor-basic form (FGF-basic) is a protein factor that is produced by many cells. It is a powerful stimulant of new cell growth and may be involved in the development of plaques in blood vessels related to coronary heart disease. It is a heparin-binding growth factor that stimulates the proliferation of a variety of cells, including mesenchymal, neuroectodermal, and endothelial cells. It is a potent mitogen for arterial smooth muscle cells and plays a pivotal role in the pathogenesis of arteriosclerosis and restenosis. Human FGF-basic also exerts a potent angiogenic activity in vivo.

FOLIC ACID(ALSO CALLED FOLATE)

Folic acid (folate) is a B vitamin involved in many metabolic reactions in the body, including new cell growth. Maternal folic acid intake has been shown to reduce the risk of neural tube defects. Low levels of folic acid may be related to anemia, nutritional disorders, and metabolic disorders and may increase the risk of high blood pressure in women. Folates are compounds of pteroylglutamic acid (PGA) that function as coenzymes in metabolic reactions involving the transfer of single-carbon units from a donor to a recipient compound. Along with vitamin B12, folate is essential for the DNA synthesis required for normal RBC maturation. Obtained from dietary sources, folate is absorbed from the small intestine and stored in the liver. Low folate intake, malabsorption, pregnancy, chronic alcoholism, and drugs such as phenytoin can cause folate deficiency. Both folate and vitamin B12 deficiency can cause macrocytic anemia. Supplementary folic acid has also been shown to reduce the risk of incident hypertension, particularly in younger women.

FOLLICLE STIMULATING HORMONE(FSH)

Follicle stimulating hormone (FSH) is a sex hormone produced in the pituitary gland. In women, increased levels of FSH are associated with menopause or a decrease in ovarian function. Increased or decreased FSH levels are also associated with a variety of glandular conditions. Follicle stimulating hormone stimulates the growth of ovarian follicles and the production of estradiol during the first half of the menstrual cycle. In the male, it stimulates the epithelium of the seminiferous tubules and is partially responsible for inducing spermatogenesis. Increased levels of FSH are associated with menopause and primary ovarian hypofunction in females, primary hypogonadism in males, alcoholism, castration, and Turner’s and Klinefelter’s syndromes. Decreased FSH levels are associated with secondary or tertiary gonadal failure in females and males caused by anorexia nervosa, hemochromatosis, and/or pituitary tumors. They are also decreased in patients treated with estrogens or androgens.

GAMMA GLUTAMYL TRANSFERASE(GGT)

Gamma glutamyl transferase (GGT) is a liver enzyme whose levels may be elevated in conditions involving liver damage. GGT levels are useful in the evaluation of obstructive liver disease, since they are more organ-specific than alkaline phosphatase (ALP). They are also elevated in chronic alcoholics, when other tests are normal, and during antiepileptic therapy. Disproportionate elevation of both ALP and GGT indicates drug-induced cholestasis.

GASTRIN

Gastrin is a digestive hormone produced by the pancreas that stimulates the production of acid in the stomach. Gastrin levels are abnormal in a variety of diseases of the digestive tract and kidneys. Too much gastrin can cause severe peptic ulcer disease. Gastrin is secreted by the G-cells of the pancreas and stimulates the parietal cells of the fundus to produce gastric acid. It also stimulates gastrointestinal motility and the production of pepsinogens, intrinsic factor, secretin, pancreatic HCO3 and enzymes, and hepatic bile. Gastrin assays are helpful in the identification of Zollinger-Ellison tumors (gastrinomas) and other causes of hypergastrinemia. Hypergastrinemia may also occur in patients with normal or slightly increased gastric acid secretion, including patients with achlorhydria (atrophic gastritis or pernicious anemia), renal insufficiency, massive small bowel resection, G-cell hyperplasia, gastric outlet obstruction, and retained gastric antrum, as well as in patients receiving potent antisecretory drugs.

GLOBULIN(GLOB)

Globulins are roughly divided into alpha, beta, and gamma globulins. High globulin levels may indicate heart or liver disease or chronic inflammation, while low levels may indicate immune system dysfunction.

GLUCOSE

Most dietary carbohydrate is converted into glucose in the body. Glucose is a major source of energy for most body cells. Its blood level is regulated by insulin and a number of other hormones. Glucose levels are most commonly measured to diagnose diabetes or to monitor diabetes treatments. Blood glucose is regulated within narrow limits by insulin, but also by glucagon, cortisol, and epinephrine. Fasting glucose levels of >_ 126 mg/dL or 2-h postprandial glucose levels of >_ 200 mg/dL are supportive of the diagnosis of diabetes mellitus.

GLUTATHIONE S-TRANSFERASE(GST)

These enzymes are important in metabolizing various compounds, including drugs, and in detoxifying cancer-causing agents. Glutathione S-transferases are a family of multifunctional enzymes that use glutathione in reactions contributing to the transformation of a wide range of compounds, including carcinogens, therapeutic drugs, and products of oxidative stress, playing a key role in cellular detoxification.

GRANULOCYTE MACROPHAGE COLONY STIMULATING FACTOR(GM-CSF)

Granulocyte macrophage colony stimulating factor (GM-CSF) is a protein that stimulates the production of white blood cells that are important in fighting serious infection. Low levels of GM-CSF may be seen in patients prone to infection. GM-CSF is an acidic glycoprotein produced in response to a number of inflammatory mediators by mesenchymal cells in the hemopoietic environment and at peripheral sites of inflammation. GM-CSF stimulates the production of neutrophilic granulocytes, macrophages, and mixed granulocyte- macrophage colonies from bone marrow cells and can stimulate the formation of eosinophil colonies from fetal liver progenitor cells. It can also affect some functional activities in mature granulocytes and macrophages. Clinically, recombinant GM-CSF is used to accelerate recovery from neutropenia and to prevent infection in cancer chemotherapy patients, AIDS patients, and persons with rare leukocyte disorders.

GROWTH HORMONE(GH)

Growth hormone (also called somatotropin) is a hormone produced in the anterior pituitary gland that regulates growth. This hormone is measured when there is abnormal growth in adults or children or when there is a history of a pituitary problem. Human growth hormone (GH, hGH, somatotropin) is the main regulator of somatic postnatal growth. It stimulates the release of somatomedin (also called IGF-I) by the liver, which causes growth. Basal GH levels in normal individuals are usually less than 2 ng/ml and are stable throughout the day. Normal elevations occur following meals, after exercise, and during sleep. Children who fail to grow at the expected rate and who have short stature with apparent normal body proportions often have a diminished capacity (congenital or acquired) to secrete growth hormone. Growth hormone deficiency in both adults and children may be the direct result of neoplastic or infiltrative disease of the pituitary or may follow cranial irradiation for brain tumors and other neoplasms.

HAPTOGLOBIN

Haptoglobin is a protein that binds to hemoglobin in the blood. Haptoglobin levels may be elevated in certain anemias, cancers, and acute inflammatory diseases. Decreased levels are seen in liver disease as well as certain anemias (hemolytic and sickle cell). It is an acute phase protein used in the detection of in vivo hemolysis. Its primary function is the irreversible binding of free oxyhemoglobin in plasma. This complex is then removed within minutes by the reticuloendothelial system, preventing loss of hemoglobin to urine and conserving iron.

HEAT SHOCK COGNATE PROTEIN 70 ANTIBODY(HSC-70)

Heat shock proteins (also called stress proteins) inside cells become more active when the cell is exposed to increased temperature or other kinds of cell stress (such as toxins, infection, or lack of oxygen). They have several functions that help the cell to recover from stress and repair stress-induced damage. Antibodies against these proteins may indicate that a patient is at increased risk of certain disorders. Functions of heat shock proteins (stress proteins) include stabilization and re-folding of proteins within the cell and various immunomodulatory activities outside it. Recent research indicates that they can induce pro-inflammatory responses and down-regulate pathogenic processes and may have a potential role as therapeutic agents. Heat shock protein 70 (HSP-70) belongs to a family of proteins that contains both heat-inducible and constitutively expressed members; the latter are sometimes called heat shock cognate proteins (HSCs). HSC-70 protein binds to nascent polypeptides to facilitate correct folding and functions as an ATPase in the disassembly of clathrin-coated vesicles during transport of membrane components through the cell.

HEAT SHOCK PROTEIN 32 ANTIBODY(HSP 32 Ab)

Heat shock proteins (also called stress proteins) inside cells become more active when the cell is exposed to increased temperature or other kinds of cell stress (such as toxins, infection, or lack of oxygen). They have several functions that help the cell to recover from stress and repair stress-induced damage. Antibodies against these proteins may indicate that a patient is at increased risk of certain disorders. Functions of heat shock proteins (stress proteins) include stabilization and re-folding of proteins within the cell and various immunomodulatory activities outside it. Recent research indicates that they can induce pro-inflammatory responses and down-regulate pathogenic processes and may have a potential role as therapeutic agents. Heat shock protein 32 appears to have a protective role in renal diseases such as glomerulonephritis and drug-induced nephrotoxicity.

HEAT SHOCK PROTEIN 65 ANTIBODY(HSP 65 Ab)

Heat shock proteins (also called stress proteins) inside cells become more active when the cell is exposed to increased temperature or other kinds of cell stress (such as toxins, infection, or lack of oxygen). They have several functions that help the cell to recover from stress and repair stress-induced damage. Antibodies against these proteins may indicate that a patient is at increased risk of certain disorders. Functions of heat shock proteins (stress proteins) include stabilization and re-folding of proteins within the cell and various immunomodulatory activities outside it. Recent research indicates that they can induce pro-inflammatory responses and down-regulate pathogenic processes and may have a potential role as therapeutic agents. Elevated levels of circulating antibody to heat shock protein 65 have been reported in carotid atherosclerosis, coronary heart disease, and borderline hypertension, but the physiological significance of these antibodies is not yet well understood.

HEAT SHOCK PROTEIN 71 ANTIBODY(HSP 71 Ab)

Heat shock proteins (also called stress proteins) inside cells become more active when the cell is exposed to increased temperature or other kinds of cell stress (such as toxins, infection, or lack of oxygen). They have several functions that help the cell to recover from stress and repair stress-induced damage. Antibodies against these proteins may indicate that a patient is at increased risk of certain disorders. Functions of heat shock proteins (stress proteins) include stabilization and re-folding of proteins within the cell and various immunomodulatory activities outside it. Recent research indicates that they can induce pro-inflammatory responses and down-regulate pathogenic processes and may have a potential role as therapeutic agents. Elevated levels of circulating antibody to heat shock protein 71 have been observed in children with immune thrombocytopenic purpura and in adults with acute heat-induced illnesses (heat cramps, heat stroke, and heat exhaustion) and benzene poisoning.

HEAT SHOCK PROTEIN 90 ALPHA ANTIBODY(HSP 90 ALPHA Ab)

Heat shock proteins (also called stress proteins) inside cells become more active when the cell is exposed to increased temperature or other kinds of cell stress (such as toxins, infection, or lack of oxygen). They have several functions that help the cell to recover from stress and repair stress-induced damage. Antibodies against these proteins may indicate that a patient is at increased risk of certain disorders. Functions of heat shock proteins (stress proteins) include stabilization and re-folding of proteins within the cell and various immunomodulatory activities outside it. Recent research indicates that they can induce pro-inflammatory responses and down-regulate pathogenic processes and may have a potential role as therapeutic agents. Elevated levels of circulating antibody to heat shock protein 90 alpha have been seen in individuals with acute heat-induced illnesses (heat cramps, heat stroke, and heat exhaustion), breast cancer, late-stage ovarian cancer, Guillain-Barré syndrome, graft-versus-host disease, systemic lupus erythematosus, and lupus nephritis, among other disorders.

HELICOBACTER PYLORI IgG ANTIBODY(H. PYLORI IgG Ab)

Helicobacter pylori (H. pylori IgG) is a bacterium responsible for the majority of stomach ulcers and many cases of chronic gastritis. Antibodies against H. pylori indicate prior infection with this bacterium. H. pylori, a common and normal inhabitant of the mucus layer of the human stomach, plays an important role in gastroduodenal inflammatory and neoplastic diseases. H. pylori antibodies are detectable in almost all adult patients with duodenal ulcers and in about 80% of patients with gastric ulcers. Infection occurs through person-to-person contact or contaminated water or food. The prevalence of H. pylori antibodies increases with age; they are more commonly found in developing countries with poor sanitation.

HEMATOCRIT

The hematocrit is the percentage of whole blood that comprises red blood cells. It is a measure of both the number and the size of these cells and is expressed as a percentage by volume. The normal ranges are age-dependent up to adolescence and gender-dependent after adolescence. A low hematocrit may indicate anemia, blood loss, bone marrow failure, destruction of red blood cells, malnutrition or specific nutritional deficiency, multiple myeloma, or rheumatoid arthritis. A high hematocrit may indicate dehydration due to burns or diarrhea, eclampsia, erythrocytosis, or polycythemia vera.

HEMOGLOBIN(Hb)

Hemoglobin (Hb) is an iron-containing protein that enables red blood cells to carry oxygen to tissues. Low levels of hemoglobin may indicate anemia, excessive bleeding, or nutritional deficiencies. It is a tetrameric hemoprotein found in erythrocytes, consisting of approximately 3.8% heme and 96.2% globin. As oxyhemoglobin (HbO2), it transports oxygen from the lungs to the tissues where the oxygen is readily released, and HbO2 becomes Hb. Disorders of Hb synthesis include structurally abnormal hemoglobins (hemoglobinopathies, the most common being sickle cell anemia) and thalassemias (in which structurally normal hemoglobins are synthesized at a lower rate, or not at all).

HEMOGLOBIN A1c(HbA1c)

Hemoglobin A1c (HbA1c) measures the amount of glucose bound to hemoglobin and indicates the general control of glucose levels in a diabetic patient over 2 to 3 months. HbA1c, also known as glycated hemoglobin or glycosylated hemoglobin, is formed when glucose in the blood binds irreversibly to hemoglobin to form a stable complex. Since the normal life span of erythrocytes is 90 to 120 days, HbA1c is eliminated only when red cells are replaced. Thus, HbA1c values are directly proportional to the concentration of glucose in the blood over the full life span of the red blood cells and are not subject to the fluctuations seen with daily blood glucose monitoring. In patients with uncontrolled diabetes, the ratio of HbA1c to non-glycated hemoglobin is higher than in non-diabetics or diabetics with good glucose control.

HEPATITIS A ANTIBODY(HAV-Ab)

Hepatitis A (HAV-Ab) is a virus that causes infectious hepatitis (inflammation of the liver). The presence of the antibody to hepatitis A virus indicates recent infection or exposure. Hepatitis A virus (HAV) is a small RNA virus belonging to the Picornaviridae family. It is spread primarily through food or water contaminated by feces from an infected person and rarely through contact with infected blood. It can cause widespread outbreaks of disease or sporadic cases of acute hepatitis, which usually resolve without treatment over several weeks. Hepatitis A outbreaks can occur among intravenous drug users, homosexual men, and hemophiliacs receiving Factors VIII and IX concentrates. Hepatitis A has an incubation period of about 4 weeks, is generally mild to moderate in severity (and usually asymptomatic in young children), and never becomes chronic. Most of the rare cases of acute liver failure due to HAV are associated with older age or underlying chronic liver disease. HAV-specific IgM antibodies are almost always present by the time symptoms of acute hepatitis appear.

HEPATITIS B CORE ANTIBODY(ANTI-HBc)

The body produces hepatitis B core IgM antibody (Anti-HBc) in response to the core antigen, but the antibody does not have a protective role in defense against the virus. Hepatitis B core antigen is derived from the protein envelope that encloses the viral DNA. A positive hepatitis B core IgM antibody test indicates past or present infection with hepatitis B but could also be a false- positive. Interpretation of this test result depends on the results of the hepatitis B surface antigen test. Its appearance with the protective surface antibody (HbsAb) indicates prior infection and recovery. In chronically infected persons, it will usually appear with the surface antigen (HbsAg).

HEPATITIS B e ANTIBODY(ANTI-HBe)

Hepatitis B e antigen is closely associated with the nucleocapsid of hepatitis B virus. Hepatitis B e antibody (anti-HBe) is the antibody that is produced in response to this antigen. During the acute stage of infection, the seroconversion from e antigen to e antibody is prognostic for resolution of infection. Presence of anti-HBe in serum along with anti-HBc and the absence of HBs antigen and anti-HBs indicate low contagiousness and convalescence.

HEPATITIS B SURFACE ANTIBODY(ANTI-HBs)

Hepatitis B surface antigens are molecules on the outer surface of the hepatitis B virus that trigger an antibody response. Hepatitis B surface antibody (anti-HBs) is the specific antibody to hepatitis B surface antigen. Anti-HBs in serum within 1 to 4 months after onset of symptoms indicate clinical recovery. Anti-HBs can provide protection against hepatitis B infection.

HEPATITIS B SURFACE ANTIGEN(HBsAg)

Hepatitis B surface antigens (HBsAg) are molecules on the outer surface of the hepatitis B virus that trigger an antibody response. A positive HBsAg test result indicates infection with the hepatitis B virus. Persistent presence of this antigen may indicate chronic infection. Hepatitis B virus (HBV) belongs to the Hepadnaviridae family. Most cases are transmitted through transfusion of HBV-contaminated blood and blood products, sexual contact, or from mother to newborn at birth. It can also be transmitted via needle sticks, body piercing, and tattooing using unsterilized instruments. HBsAg is the first serological marker detected, at a mean of 4 to 12 weeks after exposure, and levels peak before onset of symptoms. It is usually present for 2 to 3 months, but 5% to 10% of patients will have persistent HBsAg levels beyond 6 months (chronic carriers).

HEPATITIS C ANTIBODY

Hepatitis C virus (HCV) is generally transmitted through contact with infected blood products. The presence of the antibody against hepatitis C indicates recent infection or exposure. Hepatitis C virus, an RNA virus belonging to a distinct genus in the Flaviviridae family, is transmitted most efficiently via a parenteral route and is the most common chronic blood-borne infection in the United States. Blood transfusions were the leading route of transmission until routine blood screening began in 1991. In the U.S., most newly acquired hepatitis C infections are related to intravenous drug use. Risk of sexual transmission is low and occurs in < 5% of those couples in which one individual is infected. Mother-to-baby transmission is possible, but uncommon. Acute hepatitis C is asymptomatic in a majority of cases but results in chronic infection in 80% to 85% of patients. Hepatitis C is the most important cause of chronic liver disease in the U.S., with an estimated 3.9 million HCV-infected individuals. Clinical manifestations of chronic infection vary greatly; about 10% of patients develop liver cirrhosis over a 20-year period, and these patients are at risk for hepatocellular carcinoma. For those exposed to hepatitis C, the pattern of antibody formation is the primary method to assess the stage of disease.

HEPATITIS D ANTIBODY

Hepatitis D virus is strongly associated with hepatitis B virus infections. The presence of the antibody against hepatitis D indicates recent infection or exposure. Infection with the hepatitis delta virus (hepatitis delta-agent, HDV) is always seen in association with hepatitis B virus (HBV) infection, either as a simultaneous acute infection or as an acute super-infection superimposed upon chronic HBV hepatitis. HDV is an RNA virus that requires the presence of HBV for viral replication to occur. Patients almost invariably have detectable hepatitis B surface antigen (HBsAg) and/or antibodies to hepatitis core antigen (anti-HBc) and hepatitis B e antigen. In patients with acute co-infections, hepatitis D antigen (HDVAg) appears early after HBsAg and disappears with convalescence. Acute HDV infections are associated with anti-HDV IgM antibody, and chronic cases usually only demonstrate IgG antibody. Both antibodies may eventually disappear following convalescence.

HEPATITIS E orf 2.3 kD ANTIBODY(HEV orf 2.3 kD Ab)

Hepatitis E virus (HEV) is a major cause of water-borne acute hepatitis in Asia, Africa, and Mexico. The presence of the antibody against hepatitis E virus indicates recent infection or exposure. HEV transmission is via the fecal-oral route, presumably through contaminated water supplies; it often occurs among individuals 15 to 40 years of age and is usually not chronic. The highest rate of symptomatic disease (jaundice) occurs in hepatitis E outbreaks. Subclinical, non-icteric forms are rare but possible. Sporadic cases of hepatitis E in industrialized, non-endemic countries are occasionally reported. The incubation period following HEV exposure ranges from 15 to 60 days. In endemic areas, fulminant hepatitis due to HEV is highly associated with pregnancy, particularly with infections during the third trimester of pregnancy. Maternal hepatitis E fatality can reach 40%, while in the general population, the mortality rate for acute HEV infection is 0.5% to 4.0%. The duration of anti-HEV IgG persistence and the natural history of protective immunity to HEV are not well-known.

HEPATITIS E orf 2.6 kD ANTIBODY(HEV orf 2.6 kD Ab)

Hepatitis E virus (HEV) is a major cause of water-borne acute hepatitis in Asia, Africa, and Mexico. The presence of the antibody against hepatitis E virus indicates recent infection or exposure. HEV transmission is via the fecal-oral route, presumably through contaminated water supplies; it often occurs among individuals 15 to 40 years of age and is usually not chronic. The highest rate of symptomatic disease (jaundice) occurs in hepatitis E outbreaks. Subclinical, non-icteric forms are rare but possible. Sporadic cases of hepatitis E in industrialized, non-endemic countries are occasionally reported. The incubation period following HEV exposure ranges from 15 to 60 days. In endemic areas, fulminant hepatitis due to HEV is highly associated with pregnancy, particularly with infections during the third trimester of pregnancy. Maternal hepatitis E fatality can reach 40%, while in the general population, the mortality rate for acute HEV infection is 0.5% to 4.0%. The duration of anti-HEV IgG persistence and the natural history of protective immunity to HEV are not well-known.

HEPATITIS E orf 3.3 kD ANTIBODY(HEV orf 3.3 kD Ab)

Hepatitis E virus (HEV) is a major cause of water-borne acute hepatitis in Asia, Africa, and Mexico. The presence of the antibody against hepatitis E virus indicates recent infection or exposure. HEV transmission is via the fecal-oral route, presumably through contaminated water supplies; it often occurs among individuals 15 to 40 years of age and is usually not chronic. The highest rate of symptomatic disease (jaundice) occurs in hepatitis E outbreaks. Subclinical, non-icteric forms are rare but possible. Sporadic cases of hepatitis E in industrialized, non-endemic countries are occasionally reported. The incubation period following HEV exposure ranges from 15 to 60 days. In endemic areas, fulminant hepatitis due to HEV is highly associated with pregnancy, particularly with infections during the third trimester of pregnancy. Maternal hepatitis E fatality can reach 40%, while in the general population, the mortality rate for acute HEV infection is 0.5% to 4.0%. The duration of anti-HEV IgG persistence and the natural history of protective immunity to HEV are not well-known.(HEV orf 3.3 kD Ab)

HERPES SIMPLEX VIRUS TYPE 1 GLYCOPROTEIN D ANTIBODY(HSV-1 gD Ab)

Antibodies to herpes simplex virus type 1 (HSV-1) glycoprotein D indicate exposure to the most common herpes virus, which primarily causes the common cold sore, although it infrequently infects other mucous membranes. About 80% of adults carry these antibodies.

HERPES SIMPLEX VIRUS TYPES 1 AND 2 ANTIBODIES(HSV-1/2 Ab)

Herpes simplex virus type 1 (HSV-1) is the virus that causes cold sores, while herpes simplex virus type 2 (HSV-2) causes genital herpes. The presence of antibodies to either of these viruses indicates that the individual has been exposed to that virus. HSV-1 and HSV-2 can both cause systemic disease in an immunodeficient person. Antibody testing demonstrates whether an individual has been exposed to either of these viruses.

HERPES SIMPLEX VIRUS TYPE 2 GLYCOPROTEIN D ANTIBODY(HSV-2 gD Ab)

Herpes simplex virus type 2 (HSV-2) is the virus that causes genital herpes. Antibodies to HSV-2 glycoprotein D indicate exposure to the herpes virus most commonly responsible for genital infection. About 25% of adults carry these antibodies.

HIGH-DENSITY LIPOPROTEIN(HDL)

Cholesterol carried by HDL is known as the “good cholesterol” because higher levels of HDL-cholesterol are associated with a lower risk for coronary heart disease. About 25% to 30% of blood cholesterol is transported by HDL particles. By carrying excess cholesterol to the liver for “re-packaging” or excretion in the bile, HDLs help to prevent cholesterol deposition in the arteries. Low levels of HDL-cholesterol are associated with an increased risk of heart disease. Women tend to have higher HDL-cholesterol levels than men. The total cholesterol/HDL ratio is more useful in the determination of cardiovascular risk than is total cholesterol.

HISTONE ANTIBODY

Histones are normal proteins associated with the DNA in the nuclei of our cells. Antibodies to histones may be elevated in drug-induced lupus erythematosus. Autoantibodies to histones (typically IgG) occur in drug- induced lupus (DIL) in the absence of other autoantibodies and are especially reactive with histone H2A-H2B dimers when induced by procainamide. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. DIL due to procainamide, quinidine, acebutolol, penicillamine, and isoniazid, but not methyldopa, can be accompanied by autoantibodies to histone (H2A-H2B)-DNA complexes. Histones H2A and H2B (as well as H1, H3, and H4) are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis, and other syndromes.

HISTONE H1 ANTIBODY

Antibodies to histones may develop in drug-induced lupus erythematosus. This is a form of autoimmune disease. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. Histones H1, H2A, H2B, H3, and H4 are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis, and other syndromes.

HISTONE H2A ANTIBODY

Histones are normal proteins associated with the DNA in the nuclei of our cells. Autoantibodies to histones (typically IgG) occur in drug-induced lupus (DIL) in the absence of other autoantibodies and are especially reactive with histone H2A-H2B dimers when induced by procainamide. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. DIL due to procainamide, quinidine, acebutolol, penicillamine, and isoniazid, but not methyldopa, can be accompanied by autoantibodies to histone (H2A-H2B)-DNA complexes. Histones H2A and H2B (as well as H1, H3, and H4) are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis, and other syndromes. Histone (H2A-H2B)-DNA complex autoantibodies react strongly with native chromatin and are present in significantly fewer American SLE patients (50%) than Asian SLE patients (70%). They are also present in patients with scleroderma-related diseases. In procainamide-induced lupus, the sensitivity of IgG histone (H2A-H2B)-DNA complex autoantibodies is 84% at the time of diagnosis, but substantially lower after immunosuppressive or anti-inflammatory treatment.

HISTONE H2B ANTIBODY

Histones are normal proteins associated with the DNA in the nuclei of our cells. Autoantibodies to histones (typically IgG) occur in drug-induced lupus (DIL) in the absence of other autoantibodies and are especially reactive with histone H2A-H2B dimers when induced by procainamide. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. DIL due to procainamide, quinidine, acebutolol, penicillamine, and isoniazid, but not methyldopa, can be accompanied by autoantibodies to histone (H2A-H2B)-DNA complexes. Histones H2A and H2B (as well as H1, H3, and H4) are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis and other syndromes. Histone (H2A-H2B)-DNA complex autoantibodies react strongly with native chromatin and are present in significantly fewer American SLE patients (50%) than Asian SLE patients (70%). They are also present in patients with scleroderma-related diseases. In procainamide-induced lupus, the sensitivity of IgG histone (H2A-H2B)-DNA complex autoantibodies is 84% at the time of diagnosis, but substantially lower after immunosuppressive or anti-inflammatory treatment.

HISTONE H3 ANTIBODY

Histones are normal proteins associated with the DNA in the nuclei of our cells. Antibodies to histones may develop in drug-induced lupus erythematosus. Autoantibodies to histones (typically IgG) occur in drug-induced lupus (DIL) in the absence of other autoantibodies and are especially reactive with histone H2A-H2B dimers when induced by procainamide. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. Histones H1, H2A, H2B, H3, and H4 are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis, and other syndromes.

HISTONE H4 ANTIBODY

Histones are normal proteins associated with the DNA in the nuclei of our cells. Antibodies to histones may develop in drug-induced lupus erythematosus. Autoantibodies to histones (typically IgG) occur in drug-induced lupus (DIL) in the absence of other autoantibodies and are especially reactive with histone H2A-H2B dimers when induced by procainamide. Histone autoantibody concentrations often decrease when the culprit drug is avoided. Broadly reactive histone H1-H4 autoantibodies of the IgM isotype are common in systemic lupus erythematosus (SLE) and in asymptomatic individuals taking various medications. Histones H1, H2A, H2B, H3, and H4 are recognized by separate populations of histone autoantibodies in SLE, DIL, juvenile rheumatoid arthritis, and other syndromes.

HOMOCYSTEINE

Homocysteine is an amino acid found in the blood, the elevation of which may increase the risk for coronary heart disease. Homocysteine is a sulfur- containing amino acid that exists in both free (trace) and bound (98% to 99%) forms in the blood. Impaired enzyme function, as a result of genetic mutations or deficiency of essential vitamin cofactors, can lead to elevated homocysteine concentrations in circulation. Elevation of the level of homocysteine in the plasma has been linked to cardiovascular disease (including myocardial infarction, stroke, thromboembolic disease, and intermittent claudication), even in people with normal cholesterol levels, and (in pregnant women) to fetal neural tube defects. It is important to note, however, that a causal link between elevated homocysteine and these disorders has not been established.

HUMAN CHORIONIC GONADOTROPIN(Beta-hCG)

Beta human chorionic gonadotropin (Beta-hCG) is a hormone whose levels become elevated early in pregnancy (1 to 2 days after implantation of the fertilized egg in the uterus or about 10 days after ovulation). The test is most often used to confirm a pregnancy, but serum beta-hCG may also be increased in women with certain types of ovarian tumors or in men with testicular tumors. Blood or urine beta-hCG tests usually suffice for detection of normal pregnancy when it has progressed about 10 days beyond ovulation. Produced by the placental trophoblastic cells, beta-hCG’s most important role appears to be stimulation of ovarian secretion of the estrogen and progesterone required for the integrity of conceptus during the first trimester. Beta-hCG levels drop at the beginning of the second trimester as the placenta begins to produce enough progesterone to maintain the endometrium. Elevated levels of beta- hCG may indicate choriocarcinoma of the uterus, hydatidiform mole of the uterus, normal pregnancy, ovarian cancer, or testicular cancer. False-positive results occur in men with solitary testes.

HUMAN PAPILLOMA VIRUS ANTIBODY(HPV Ab)

Human papilloma virus (HPV) is the most commonly sexually transmitted organism. It is the cause of genital warts and may increase the risk of cervical cancer. The presence of the antibody to HPV indicates recent infection with the virus. HPV is an icosahedral DNA virus of the genus Papillomavirus, family Papovaviridae. Many serotypes have been described; some cause cutaneous and genital warts, while others are associated with severe cervical intraepithelial neoplasia and anogenital and laryngeal carcinomas. Exposure to HPV can be determined by testing the serum for antibodies to the viral capsule. Exposure to one serotype does not prevent infection from another; in fact, one study looking at seropositivity to HPV type 16 found a 30% incidence of multiple HPV type positivity.

HUMAN T-CELL LYMPHOTROPIC VIRUS TYPES 1 AND 2 ANTIBODIES(HTLV-1/2 Ab)

Human T-cell lymphotropic virus (HTLV) is a virus that may be associated with T-cell leukemias and lymphomas. The presence of antibodies against HTLV-1 or HTLV-2 may indicate exposure or infection. Human T-lymphotropic virus types 1 (HTLV-1) and 2 (HTLV-2) differ in pathogenicity. HTLV-1 causes leukemia and other neurologic and inflammatory diseases, whereas HTLV-2 is less clearly associated with specific diseases. HTLV antibodies have been detected in family members of patients with HTLV-associated disease.

IMMUNOGLOBULIN A(IgA)

Secretory immunoglobulin A (IgA) is found in tears, sweat, saliva, mother’s milk and colostrum, and in gastrointestinal and bronchial secretions. It protects the mucosa from bacteria and viruses. The presence of secretory IgA also affects the development of allergic (IgE) reactions to various ingested antigens by binding the antigens and preventing IgE responses. Elevated serum IgA is common in patients with skin, gut, respiratory, and renal infections, or AIDS. IgA (and sometimes IgG) are also elevated in portal cirrhosis. IgA deficiency is found in 1 in 750 individuals.

IMMUNOGLOBULIN E(IgE)

Immunoglobulin E (IgE) antibodies are a class of proteins that are often involved in allergic reactions. Significant elevations in IgE levels may indicate an allergic reaction, parasitic infection, or immune disorder. The levels of circulating IgE in serum are low (<0.1%) compared with levels of the other immunoglobulins. Levels at birth are almost non-detectable but increase with age. Serum IgE levels are elevated in individuals with multiple myeloma and severe allergic reactions, and IgE serum assays are useful in monitoring treatment of these disorders. However, low levels of circulating IgE do not necessarily indicate the absence of allergic disease, since certain individuals have low total IgE levels but a high concentration of allergen-specific IgE. Investigators have shown that increased IgE levels in cord blood and infant’s serum may predict the early onset of allergic disease. Patients with pulmonary aspergillosis, parasitic infestations, and some immunodeficiencies have also been found to have elevated IgE levels.

IMMUNOGLOBULIN M(IgM)

IgM antibodies are a class of proteins produced by the immune system early in an immune reaction. IgM levels therefore usually rise in acute infections, particularly viral infections. Substantially elevated serum IgM levels may indicate a variety of blood cell disorders. In adults, IgM accounts for about 10% of the total serum antibodies. IgM deficiency may be due to protein loss, primary inherited defects, toxins (e.g., drugs or substances retained in renal failure), or secondary to lymphoid malignancies. IgM antibodies tend to predominate in primary viral infections and bloodstream infections (e.g., malaria), and IgM levels are markedly increased in primary biliary cirrhosis. In intrauterine infections, fetal production of IgM increases, and at birth, IgM levels in cord blood are increased. High levels of plasma IgM are also seen in patients with Waldenström’s macroglobulinemia and monoclonal cryoglobulinemias.

INFLUENZA A ANTIBODY

Influenza is a viral disease characterized by fever, muscle aches, headache, sore throat, fatigue, and sometimes cough. Influenza type A is the most common type of virus to cause “the flu.” The presence of antibodies to influenza A indicates exposure to or infection with this virus. Levels of these antibodies may be elevated after getting the flu vaccine. Influenza type A virus can infect a wide variety of animals, including horses, poultry, and swine. Of the three types of influenza viruses, type A is most likely to cause epidemics and pandemics because it can undergo antigenic drift (gradual viral evolution) and shift (abrupt changes in viral hemagglutinin and/or neuraminidase proteins) and present a new immune target to susceptible individuals. The influenza A antibody test determines whether exposure to or vaccination with influenza A has occurred.

INFLUENZA A H3N2 ANTIBODY

Influenza is a viral disease characterized by fever, muscle aches, headache, sore throat, fatigue, and sometimes cough. Influenza type A is the most common type of virus to cause “the flu,” and H3N2 is a common subtype of this virus. The presence of antibodies to influenza A H3N2 indicates recent exposure to or infection with this virus. Levels of these antibodies may be elevated after getting the flu vaccine. Influenza type A virus can infect a wide variety of animals, including horses, poultry, and swine. Of the three types of influenza viruses, type A is most likely to cause epidemics and pandemics because it can undergo antigenic drift (gradual viral evolution) and shift (abrupt changes in viral hemagglutinin and/or neuraminidase proteins) and present a new immune target to susceptible individuals. Type A viruses are divided into subtypes based on differences in hemagglutinin and neuraminidase proteins; current subtypes are designated A (H2N1) and A (H3N2). This test determines whether exposure to or vaccination with influenza A, subtype H3N2, has occurred.

INFLUENZA B ANTIBODY

Influenza is a viral disease characterized by fever, muscle aches, headache, sore throat, fatigue, and sometimes cough. Influenza type A and influenza type B are common viruses that can cause “the flu.” Although both types may cause widespread infection, influenza B infections are often limited to localized outbreaks. The presence of antibodies to influenza B indicates exposure to or infection with this virus. Levels of these antibodies may be elevated after getting the flu vaccine. Influenza type B virus infects only humans and can cause widespread disease. However, since this virus undergoes relatively slow changes in viral hemagglutinin proteins (unlike the type A virus), it is less frequently the cause of influenza epidemics. Nonetheless, influenza B virus is currently included in the influenza vaccine, and antibody levels may be elevated following vaccination. The pattern of antibody to the various serotypes of influenza can provide useful information regarding the history of exposure.

INSULIN

Insulin is a hormone made by the pancreas that regulates the amount of sugar (glucose) in the blood and allows cells to use this sugar for energy. Diabetes occurs when the body fails to produce enough insulin or when the body’s cells cannot respond to it efficiently. Insulin levels may be monitored in patients suspected of having low blood sugar (hypoglycemia) or high insulin levels (hyperinsulinemia), the latter being common in certain diseases, including insulin resistance syndrome and polycystic ovarian syndrome. Insulin circulates in inappropriately high levels in patients with insulin-secreting pancreatic tumors (insulinomas) resulting in hypoglycemia. Accordingly, insulin immunoassays, sometimes used in connection with a provocative dose of tolbutamide or calcium, play an essential role in the identification (and localization) of these tumors. Diabetes, obesity, a high-carbohydrate diet, and inactivity all tend to increase insulin levels, and elevated levels are found in acromegaly, Cushing’s syndrome, thyrotoxicosis, and polycystic ovarian syndrome.

INSULIN ANTIBODY

Antibodies against insulin may develop in patients receiving insulin injections for the treatment of diabetes. This may make them somewhat resistant to insulin’s effects. In patients who have never received insulin injections, antibodies against insulin may indicate an autoimmune condition leading to the destruction of the insulin-producing cells in the pancreas. This could result in the development of diabetes. The presence of insulin autoantibodies (antibodies against insulin in patients never treated with it) is evidence of the ongoing destruction of islet cells. When present in sufficient quantities, insulin antibodies can cause insulin resistance or stimulate inappropriate insulin release. Insulin antibody levels are useful when a change in insulin source is being considered or when the patient is not responding predictably to insulin therapy.

INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN 3(IGFBP3)

IGF binding protein 3 is a protein hormone whose structure resembles that of insulin. Functionally, it is related to growth hormone and may be important in the normal development of children. Insulin-like growth factors (IGF-1 and IGF-2) are peptides structurally similar to insulin, which exhibit growth- promoting as well as insulin-like and mitogenic effects. Circulating IGF-1 is almost totally bound to IGF binding proteins (IGFBPs), 6 of which have been identified. IGFBP3 is the major carrier of IGFs in serum and is present in the highest concentrations. Serum concentrations are fairly constant throughout the day and are controlled by growth hormone (GH) and IGF-1 levels. The measurement of IGFBP3 is useful in the evaluation of short stature in children, acromegaly, the efficacy of treatment for GH deficiency, the surgical cure of somatotroph tumors, and nutritional status. Because IGFBP3 levels are less age-dependent (and higher in young children) than IGF-1 levels, they allow for better differentiation between normal and subnormal levels. IGFBP3 levels also show a better correlation with GH sufficiency than do single measurements of IGF-1 or IGF-2. Although originally defined as the principal carrier of IGF-1 in the circulation and the primary regulator of the amount of free IGF-1 available to interact with the IGF-1 receptor, evidence is accumulating that IGFBP3 can also cause apoptosis in an IGF-independent manner, suggesting that its ultimate function may be to protect against the potentially carcinogenic effects of growth hormone and IGF-1.

INSULIN-LIKE GROWTH FACTOR-1(IGF-1)

Insulin-like growth factor-1 (IGF-1) is a protein hormone similar in structure and function to insulin, but with a much higher growth-promoting activity than insulin. It stimulates proliferation and survival of various cell types including muscle, bone, and cartilage tissue in vitro. IGFs are predominantly produced in the liver, although a variety of tissues produce IGFs at distinctive times. Circulating IGF-1 is almost totally protein-bound to IGF binding proteins (IGFBPs).

INTERCELLULAR ADHESION MOLECULE-1(ICAM-1)

Intercellular adhesion molecule-1 (ICAM-1) is a cell surface adhesion molecule whose levels may be elevated in several diseases, including chronic inflammatory conditions, cardiovascular disease, HIV, asthma, diabetes, and cancer. ICAM-1 (also called CD54) is a cell surface adhesion molecule that is implicated in a number of cellular processes. It can be expressed on non-hematopoietic cells, including vascular endothelial cells, thymic epithelial cells, other epithelial cells, and fibroblasts, as well as on hematopoietic cells such as tissue macrophages, mitogen-stimulated T-lymphoblasts, germinal center B-cells, and dendritic cells in the tonsils, lymph nodes, and Peyer’s patches. Its soluble form is a product of cleavage at the cell’s surface and may have either positive or negative feedback functions.

INTERLEUKIN-1 ALPHA(IL-1 ALPHA)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-1 alpha (IL-1 alpha) controls certain immune system reactions, including inflammation, swelling, fever, and shivering. IL-1 stimulates T-cells to secrete IL-2 and activate the inflammatory response. It also causes the hypothalamus to increase the body temperature. The two distinct forms of the protein, IL-1 alpha and IL-1 beta, perform the same functions but are structurally quite distinct. Biological effects of IL-1 include replacing macrophage requirements for T-cell activation, inducing fever and shivering, promoting prostaglandin production, promoting leukocyte growth, augmenting corticosteroid release, promoting hematopoesis, and promoting wound healing. Peripheral blood mononuclear cells of patients with aplastic anemia show markedly decreased IL-1 levels, although myelodysplastic patients with comparable degrees of pancytopenia have normal IL-1 production. Elevated IL-1 levels are found in the synovial fluid of patients with rheumatoid arthritis and osteoarthritis. In addition, IL-1 alpha may contribute to the pathogenesis of vascular occlusion and injury.

INTERLEUKIN-1 BETA(IL-1 BETA)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-1 beta (IL-1 beta) controls certain immune system reactions, including inflammation, swelling, fever, and shivering. IL-1 stimulates T-cells to secrete IL-2 and activate the inflammatory response. It also causes the hypothalamus to increase the body temperature. The two distinct forms of the protein, IL-1 alpha and IL-1 beta, perform the same functions but are structurally quite distinct. Biological effects of IL-1 include replacing macrophage requirements for T-cell activation, inducing fever and shivering, promoting prostaglandin production, promoting leukocyte growth, augmenting corticosteroid release, promoting hematopoesis, and promoting wound healing. Peripheral blood mononuclear cells of patients with aplastic anemia show markedly decreased IL-1 levels, although myelodysplastic patients with comparable degrees of pancytopenia have normal IL-1 production. Elevated IL-1 levels are found in the synovial fluid of patients with rheumatoid arthritis and osteoarthritis. Unlike IL-1 alpha, which is intracellular until cell death, IL-1 beta is secreted outside the cell.

INTERLEUKIN-2(IL-2)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-2 (IL-2) is important in anti-inflammatory reactions, blood cell production, and elimination of cancer cells at an early stage of cancer development. Its levels may be elevated in a number of inflammatory conditions as well as various forms of cancer. It stimulates the synthesis of interferon- gamma in peripheral leukocytes and induces the secretion of IL-1, tumor necrosis factor (TNF)-alpha and TNF-beta. IL-2 also supports the proliferation and clonal expansion of T-cells that specifically attack certain tumor cell types and is increasingly used to treat patients with cancers refractory to conventional treatment. A number of diseases have been found to be associated with the aberrant expression of IL-2 or IL-2 receptors, including Hodgkin’s disease, graft-versus-host disease, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes, lepromatous leprosy, AIDS, immunodeficiency syndrome, severe burns, and allogeneic bone marrow transplantation.

INTERLEUKIN-3(IL-3)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-3 (IL-3) helps to stimulate the development and functioning of various types of blood cells. Its levels may be abnormal in a variety of inflammatory and blood cell diseases. IL-3 is produced mainly by T-cells (following cell activation by antigens and mitogens) but also by keratinocytes, natural killer cells, mast cells, endothelial cells, and monocytes. It is one of the priming factors for hematopoietic stem cells in vitro and in vivo, making these cells responsive to later-acting factors such as erythropoietin, granulocyte/ macrophage colony-stimulating factor, and IL-6. IL-3 also induces the increased expression of receptors for colony-stimulating factors, induces mast cell and macrophage proliferation, and stimulates histamine synthesis by mast cells and phagocytosis by macrophages. At picomolar-to-nanomolar concentrations, IL-3 chemoattracts eosinophils and influences the chemotactic behavior of these cells in response to other chemotactically active factors. At nanomolar concentrations, it induces the expression of complement factor C3a receptors in basophils.

INTERLEUKIN-4(IL-4)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-4 (IL-4) helps to control the immune system’s response to inflammation. Its levels may be abnormal in inflammatory conditions as well as autoimmune diseases. IL-4 is produced mainly by a subpopulation of activated T-cells (Th2), which are the most active of the helper cells for B-cells and which also secrete IL-5 and IL-6 alpha. IL-4 may be useful in the treatment of inflammatory conditions and autoimmune diseases since it inhibits the production of inflammatory cytokines such as IL-1, IL-6, and tumor necrosis factor. It may also be useful in the treatment of solid tumors, hematopoietic diseases, and immune defects; it inhibits the growth of colon and mammary carcinomas and augments the development of lymphokine- activated killer cells. IL-4 may play an essential role in the pathogenesis of chronic lymphocytic leukemia.

INTERLEUKIN-5(IL-5)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-5 (IL-5) is produced by T-cells (a type of white blood cell) and is specifically responsible for the growth and maturation of eosinophils (another type of white blood cell). Its levels may be abnormal in certain infectious and inflammatory disorders. IL-5 also promotes the generation of cytotoxic T-cells from thymocytes. A possible clinical application is suggested by its effect on eosinophils; animal experiments have shown that induced eosinophilia and lung infiltration by eosinophils in mice can be prevented by administration of monoclonal antibodies directed against IL-5.

INTERLEUKIN-6(IL-6)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Levels of interleukin-6 (IL-6) may be elevated in a variety of inflammatory and infectious diseases and other various stimuli. In addition to its role as an acute phase reactant and endogenous pyrogen, it is involved in B-cell differentiation into plasma cells. IL-6 is usually not detectable in serum, plasma, CSF, or joint fluid. Elevated levels are observed in a variety of inflammatory processes, including endotoxemia and collagen vascular diseases, as well as in alcoholic cirrhosis and chronic renal failure.

INTERLEUKIN-7(IL-7)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Levels of interleukin-7 (IL-7) may be elevated in a variety of inflammatory and infectious diseases. IL-7 stimulates the proliferation of pre-B- and pro-B-cells without affecting differentiation or mature B-cells. It also selectively supports the maturation of megakaryocytes and stimulates the proliferation of early and mature activated T-cells (synergized by suboptimal doses of IL-1). It stimulates the proliferation of thymocytes with certain CD markers and is therefore an important differentiation factor for functionally different T-lymphocyte subpopulations. In peripheral monocytes, IL-7 induces the synthesis of inflammatory mediators; in activated T-cells, it enhances the expression and secretion of IL-3 and granulocyte/macrophage colony- stimulating factor; and in macrophages, it down-regulates the expression of transforming growth factor (TGF)-beta.

INTERLEUKIN-8(IL-8)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-8 (IL-8) is involved in a variety of inflammatory processes and may be particularly important in psoriasis and rheumatoid arthritis. Elevated concentrations are observed in psoriatic scales, which may explain the high proliferation rate of these cells. IL-8 may also be a marker of inflammatory processes and probably plays a role in the pathogenesis of chronic polyarthritis since excessive amounts of IL-8 are found in synovial fluid.

INTERLEUKIN-10(IL-10)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-10 (IL-10) is involved in the elimination of cancer cells at an early stage of development and may suppress the growth of certain cancers, such as non-Hodgkin’s lymphoma. IL-10 is produced by, and down-regulates the function of, Th1 and Th2 cells. In macrophages stimulated by bacterial lipopolysaccharides, it inhibits the synthesis of IL-1, IL-6, and tumor necrosis factor-alpha by promoting the degradation of cytokine mRNA, and it also inhibits antigen presentation. In monocytes, interferon-gamma and IL-10 antagonize each other’s production and function. IL-10 has also been shown to be a physiologic antagonist of IL-12, and studies suggest that it indirectly suppresses the growth of certain tumors by inhibiting the infiltration of macrophages that may promote tumor growth. IL-10 has been detected in the sera of a subgroup of patients with active non-Hodgkin’s lymphoma, and levels appear to correlate with mortality in patients with intermediate or high- grade disease.

INTERLEUKIN-12 p40(IL-12 p40)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-12 (IL-12) is produced by white blood cells called lymphocytes and may help to prevent certain cancers. IL-12 levels may also be elevated in bacterial and parasitic infections. IL-12 p40 is the 40 kDa subunit of IL-12, which is secreted by peripheral lymphocytes (mainly B-cells and to a lesser extent T-cells) after induction. IL-12 may be useful in expanding an antigen- specific T-cell population and has been shown to augment natural killer cell- mediated cytotoxicity in a number of conditions, including hairy cell leukemia. Its abilities to induce the synthesis of interferon (IFN)-gamma and to stimulate the proliferation of resting peripheral cells may also be important. In vivo, IL-12 inhibits the growth of a variety of experimental tumors and has antiangiogenic effects that are at least partly mediated by IFN-gamma. Therefore, IL-12 seems to be a potential candidate in the treatment of angiogenesis-dependent malignancies.

INTERLEUKIN-12 p70(IL-12 p70)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-12 (IL-12) is produced by white blood cells called lymphocytes and may help to prevent certain cancers. IL-12 levels may also be elevated in bacterial and parasitic infections. IL-12 p70 is the 70 kDa subunit of IL-12, which is secreted by peripheral lymphocytes (mainly B-cells and to a lesser extent T-cells) after induction. IL-12 may be useful in expanding an antigen- specific T-cell population and has been shown to augment natural killer cell- mediated cytotoxicity in a number of conditions, including hairy cell leukemia. Its abilities to induce the synthesis of interferon (IFN)-gamma and to stimulate the proliferation of resting peripheral cells may also be important. In vivo, IL-12 inhibits the growth of a variety of experimental tumors and has antiangiogenic effects that are at least partly mediated by IFN-gamma. IL-12 therefore seems to be a potential candidate in the treatment of angiogenesis-dependent malignancies.

INTERLEUKIN-13(IL-13)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-13 (IL-13) controls the activity of white blood cells called macrophages and reduces the production of other cell signaling proteins, including some of the other interleukins. IL-13 is expressed in activated T-helper cells and T-cells expressing CD8. It down-modulates macrophage activity, reducing the production of pro-inflammatory cytokines (IL-1, IL-6, IL-8, IL-10, and IL-12) and chemokines (MIP-1 and MCP) in response to interferon-gamma or bacterial lipopolysaccharides. IL-13 also enhances the production of the IL-1 receptor antagonist and decreases the production of nitric oxide by activated macrophages, leading to a decrease in parasiticidal activity.

INTERLEUKIN-15(IL-15)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-15 (IL-15) controls the activity of white blood cells called macrophages and reduces the production of other cell signaling proteins, including some of the other interleukins. Some of the biological activities of IL-15 resemble those of IL-2, but IL-15 and IL-2 differ in their controls of expression and secretion, their range of target cells, and their functional activities. IL-15 stimulates proliferation of the established T-cell line CTLL-2 as well as phytohemagglutinin-stimulated peripheral blood mononuclear cells. In addition, IL-15 can induce generation of cytolytic cells and lymphokine-activated killer cells activity in vitro. IL-15 appears to function as a specific maturation factor for natural killer (NK) cells and can mimic the bone marrow microenvironment in vitro, which is required for NK cells to acquire lytic functions. IL-15 inhibits apoptosis induced by deprivation of cytokines in activated T-cells and inhibits apoptosis induced by various antibodies in a manner dependent on RNA synthesis.

INTERLEUKIN-16(IL-16)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-16 (IL-16) attracts certain white blood cells, including T-cell lymphocytes, macrophages, and eosinophils. IL-16 was originally described as lymphocyte chemoattractant factor (LCF), which chemoattracts CD4+ T-cells, macrophages, and eosinophils. It is secreted by activated CD8+ cells. Very high levels of IL-16 are produced in response to IL-1 beta.

INTERLEUKIN-18(IL-18)

Interleukins are cytokine (cell signaling) proteins produced by white blood cells, which help to control immune system and inflammation responses. Interleukin-18 (IL-18) helps to control the activity of some of the white blood cells involved in the immune response. Increased levels of IL-18 may be associated with Crohn’s disease. IL-18 is one of the pro-inflammatory cytokines. One important function is the regulation of functionally distinct subsets of T-helper cells required for cell-mediated immune responses. Abnormal expression of IL-18 has been observed in autoimmune non-obese diabetic (NOD) mice and appears to be closely associated with the development of diabetes.

IRON BINDING CAPACITY, TOTAL(TIBC)

Iron in blood is carried by the transport protein, transferrin. Total iron binding capacity measures your body’s ability to transport iron and is usually higher than normal when the body’s iron stores are low. An increased iron binding capacity (TIBC) is seen in iron deficiency states, which are often related to blood loss or anemia. In iron overload states, such as hemochromatosis, iron levels are high and TIBC is low or normal. In liver disease, TIBC and transferrin levels are low, since transferrin is made in the liver. Because transferrin levels fall relatively rapidly when there is insufficient protein in the diet, TIBC can also be used to monitor nutrition. A decreased TIBC is often seen in chronic inflammatory disorders, kwashiorkor, chronic iron overloading, and malignancies.

IRON BINDING CAPACITY, UNSATURATED(UIBC)

Unsaturated iron binding capacity (UIBC) is the reserve iron binding capacity of serum. Iron in blood is carried by the transport protein, transferrin. Only about one-third of the iron binding sites of transferrin are normally occupied by Fe (III); therefore, serum has considerable reserve iron binding capacity. UIBC levels may be used to detect hereditary hemochromatosis, or iron overload.

IRON, PERCENT SATURATED

Saturated iron binding capacity is a measure of the percentage of transferrin and other mobile, iron-binding proteins saturated with iron.

IRON, SERUM

Iron is an important mineral that is involved in the transport of oxygen in the blood. About 65% of the body’s iron are attached to hemoglobin. Iron deficiency anemia is the most common nutritional disorder in the world and is found primarily among young children and premenopausal women. Measurement of iron in serum aids in the evaluation of a number of conditions involving erythrocyte production and destruction, iron metabolism, iron transport, or nutrition. Elevated serum levels of iron may occur in hemochromatosis, hemolysis, hemolytic anemia, hemosiderosis, hepatic necrosis, hepatitis, vitamin B12 deficiency, and lead toxicity. Decreased serum iron levels may occur in iron deficiency anemia, malabsorption, nephrotic syndrome, insufficient dietary iron, and circumstances involving chronic or heavy bleeding.

JO-1 ANTIBODY

The presence of antibodies against the Jo-1 antigen occurs in various autoimmune inflammatory conditions, including myositis, interstitial lung disease, and arthritis conditions. Antibodies against the Jo-1 antigen (histidyl-tRNA synthetase) are found in about 30% of adult patients with myositis and are particularly common (about 60%) in patients with both myositis and interstitial lung disease (cryptogenic fibrosing alveolitis or pulmonary interstitial fibrosis). Jo-1 antibodies are most often found in patients with the anti-synthetase syndrome, which is characterized by an acute onset, steroid-responsive myositis with interstitial lung disease, fever, symmetrical arthritis, Raynaud’s phenomenon, and “mechanic’s hands.”

LACTATE DEHYDROGENASE(LDH)

Many different types of body cells contain the enzyme lactate dehydrogenase, particularly those in the heart, kidney, liver, and muscle. LDH levels may be abnormally high in heart attack and liver disease, as well as other diseases. LDH catalyzes the conversion of lactate to pyruvate, an important step in energy production in cells. LDH levels are used for assessment of myocardial infarction, liver disease, pernicious and megaloblastic anemia, pulmonary embolus, malignancy, and muscular dystrophy.

LEISHMANIA DONOVANI ANTIBODY(L. DONOVANI Ab)

Leishmania donovani is an infectious parasite that causes visceral leishmaniasis, including kala-azar, also known as black fever. Leishmania parasites are transmitted by the bite of female Phlebotominae sandflies. It is rarely found in the U.S. but has been reported in the states bordering Mexico.

LEPTIN

Leptin is a protein hormone, expressed primarily by fat cells, which helps to control body weight through effects on appetite centers in the brain. Typically, obese individuals have higher leptin levels. Leptin is also produced by epithelial cells in the stomach and placenta. Leptin acts on a receptor site in the ventromedial nucleus of the hypothalamus to curb appetite and increase energy expenditure as body fat stores increase. Leptin levels are 40% higher in women than in men and show a further 50% rise just before menarche, later returning to baseline levels. Serum leptin levels are lowered by fasting and increased by inflammation, and increased leptin levels are seen in obese individuals. Although mutations in both the leptin and leptin receptor genes have been found in a small number of morbidly obese human subjects with abnormal eating behavior, the majority of obese people do not show such mutations and have normal or elevated circulating leptin levels.

LIPOPROTEIN(a) [(Lp(a)]

Lipoprotein (a) [(Lp(a)] blood levels are mostly determined by inherited genes, with a heritability of about 90%. Elevated levels of LP(a) are associated with an increased risk of coronary heart disease. Lp(a) is an atherogenic plasma protein whose structure resembles that of low-density lipoprotein (LDL). Lp(a) appears to competitively inhibit plasminogen activation, thus interfering with fibrinolysis and increasing thrombogenic risk. Increased Lp(a) levels are associated with rapid progression of coronary disease and an increased risk of clinical recurrence after angioplasty.

LOW-DENSITY LIPOPROTEIN(LDL)

Cholesterol carried by low-density lipoprotein (LDL) is known as the “bad cholesterol” because higher levels of LDL-cholesterol are associated with an increased risk for coronary heart disease. LDL oxidation promotes foam cell formation (the origin of atherosclerosis) and impairs endothelial cell function. Reduction of LDL-cholesterol levels is associated with atherosclerotic regression or lack of progression on angiographic studies.

LOW-DENSITY LIPOPROTEIN/HIGH-DENSITY LIPOPROTEIN RATIO(LDL/HDL RATIO)

The low-density lipoprotein/high-density lipoprotein (LDL/HDL) ratio is the ratio of “bad cholesterol” to “good cholesterol” and is used because a high level of HDL may partially offset the negative effects of a high LDL level. A ratio of 3 represents an average risk level, while people with ratios of 2.5 or less have only half the risk of heart disease as does the population at large. Evaluation of cardiac risk requires information about total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, and ratios of LDL-cholesterol or total cholesterol to HDL-cholesterol.

LUTEINIZING HORMONE(LH)

Luteinizing hormone (LH) is a hormone released by the pituitary gland. In women, a surge of LH in the middle of the menstrual cycle first causes ovulation, then stimulates the ovaries to produce estrogen and progesterone for about a week. In men, LH stimulates the production of androgen (a male hormone) by the testes. LH is typically increased in menopausal women, women with poorly functioning ovaries, and men with poorly functioning testes. LH is synthesized in the anterior lobe of the hypophysis, and activation and secretion are controlled by gonadotropin-releasing hormone from the hypothalamus. In females, LH stimulates the ovarian theca cells to synthesize and secrete steroid hormones. It induces ovulation of the ripe follicle and formation of the corpus luteum, then remains dominant in the luteal phase in order to maintain the corpus luteum and endometrium in the event of pregnancy. In males, LH stimulates the Leydig cells to secrete testosterone. Increased levels of LH are associated with menopause, primary ovarian hypofunction, and polycystic ovarian syndrome in females, and primary hypogonadism in males. Decreased LH levels are associated with secondary and tertiary ovarian hypofunction in females and secondary hypogonadism in males.

LYME DISEASE ANTIBODY(BORRELIA BURGDORFERI ANTIBODY, B. BURGDORFERI Ab)

Borrelia burgdorferi is the bacterium that causes Lyme disease. This disease may cause many different signs and symptoms including rash, arthritis, central nervous system problems, and heart-related ailments. The presence of the antibody against Borrelia burgdorferi indicates prior or current exposure to or infection with this bacterium. Transmission of the spirochete Borrelia burgdorferi is via the bite of an infected tick of the Ixodid species. Lyme borreliosis is the most common vector-borne disease in the United States. In the majority of cases, it is easily treated and does not progress to the chronic stage; severe, long-term effects probably occur in fewer than 10% of untreated patients.

LYMPHOCYTE COUNT

Lymphocytes make up 20% to 40% of all white blood cells in the bloodstream and are part of the body’s immune system. They identify foreign substances, bacteria, and viruses in the body and produce antibodies against them. Patients with lymphocyte deficiencies may be more vulnerable to infections. Occasionally, those with an excessive number of lymphocytes are found to have a type of leukemia. Lymphocytes are produced in the bone marrow. The lymphocyte count is normally >1,000 cells/μl of blood in adults and >3,000 cells/μl in children. A variety of diseases and conditions, including HIV infection, can decrease lymphocyte numbers, although reduced numbers may not significantly decrease the total white blood cell count. Lymphocyte numbers may also fall briefly during times of severe stress and while using corticosteroids or undergoing cancer chemotherapy or radiation therapy. A severe reduction may occur in certain hereditary disorders. Insufficient B-cell numbers can lead to reduced antibody production, while insufficient T-cells or natural killer cells can cause patients to have problems overcoming certain infections, especially those caused by viruses, fungi, and parasites.

LYMPHOCYTE PERCENTAGE

Lymphocytes make up 20% to 40% of all white blood cells in the bloodstream and are part of the body’s immune system. They identify foreign substances, bacteria, and viruses in the body and produce antibodies against them. Patients with lymphocyte deficiencies may be more vulnerable to infections. Occasionally, those with an excessive number of lymphocytes are found to have a type of leukemia. Lymphocytes are produced in the bone marrow. The lymphocyte count is normally >1,000 cells/μl of blood in adults and >3,000 cells/μl in children. A variety of diseases and conditions, including HIV infection, can decrease lymphocyte numbers, although reduced numbers may not significantly decrease the total white blood cell count. Lymphocyte numbers may also fall briefly during times of severe stress and while using corticosteroids or undergoing cancer chemotherapy or radiation therapy. A severe reduction may occur in certain hereditary disorders. Insufficient B-cell numbers can lead to reduced antibody production, while insufficient T-cells or natural killer cells can cause patients to have problems overcoming certain infections, especially those caused by viruses, fungi, and parasites.

LYMPHOTACTIN

Lymphotactin is a protein that chemically attracts the white blood cells called lymphocytes. Lymphotactin is produced by activated progenitor T-cells and is characterized by specific chemotactic activity for lymphocytes, but not for monocytes or neutrophils, a characteristic that makes it unique among chemokines. Lymphotactin is produced by natural killer (NK) cells and attracts both NK cells and T-cells in vivo but does not affect the adhesiveness of NK cells to vascular endothelium. It also has the ability to inhibit immature subsets of myeloid progenitors stimulated to proliferate by multiple growth factors.