Your Immune Profile

[The following was written by Susan Hanewich, RN, BSN, of the National Institue of Allergies & Infectious Diseases (NIAID) at the National Institutes of Health (NIH) in Bethesda, MD. Sue, a wonderful person, is a study coordinator in the 8th Floor (AIDS) Clinic at NIH, involved with the testing of various treatments for AIDS and HIV infection. The material is not copyrighted, but should give credit to Sue, NIAID and NIH if published.]

I. Introduction

One of the many functions of the body is to protect itself from the invasion of foreign substances. This protective role is acted out by the immune system which is a complex network of specialized cells and organs. The success of this system in defending the body relies on an incredibly elaborate interplay of T-cells, B-cells, natural killer cells and accessary cells. It is one of the most difficult systems to assess because of its complexity. By combining a series of tests utilizing both in vivo (in the body) and in vitro measurements (in the lab) of immune function, along with determination of cell numbers, one is able to determine the function of the immune system of a given individual.

Here, in the NIAID clinic, baseline assessment of the immune response is done before initial therapy is started. These various tests will then be repeated intermittently during the therapy regimen to determine if changes are occurring. The easiest way to assess the function of various cells of the immune system is by drawing blood peripherally (from the arm) and by doing a skin test.

Besides immune profiles being done, other test are done to observe for possible complications related to the virus and most importantly to observe for possible toxicities (adverse affects) of medications given to fight the virus. These are often referred to as safety bloods and include a CBC/differential, SMAC (full chemistries) and a urinalysis. The CBC consists of the white blood cell count, hemoglobin, hematocrit and platelet count. The differential is the count of the various white cells; lymphocytes, granulocyte, and several others. The SMAC shows the functioning of the liver, kidneys, heart and many other important functions. The urinalysis helps determine the function of the kidneys. There is some overlap of safety blood and the immune profile as maybe noted. Below is a brief explanation of the various tests done for both the immune profile and for safety blood.

II. Immune Profile

A. WHITE BLOOD CELLS-WBC NORMAL VALUE: 3000-10000/cu.mm. There are many types of white blood cells (WBC). WBCs are produced in the bone marrow and stored in various lymphoid tissues such as the thymus, lymph nodes, spleen, tonsils, etc. White blood cells play a major role in defending the body against infections and foreign invaders such as bacteria, fungi, viruses and parasites. A person infected with HIV often has a lowered WBC count since the virus attacks certain white blood cells.

1. POLYMORPHONUCLEAR GRANULOCYTES- POLYS, SEGS, NEUTROPHILS, GRANS NORMAL VALUE: 40-78% of WBC or 1200-7800/cu mm. Polys are a mature white blood cell with Bands being the less mature polys. The main function of polys is phagocytic meaning that they ingest and kill bacteria and foreign matter. When the total poly count is less than 1000/cu mm., there is an increased risk for bacterial and certain fungal infections and severe risk when less than 500/cu mm. A person with HIV with HIV infection usually has a normal poly count but some medications given to fight the infection may cause a drop in the poly count.

2. LYMPHOCYTES-LYMPHS NORMAL VALUE: 14-49% of WBC or 420-4900/cu mm. Lymphocytes are small white blood cells that bear the major responsibility for carrying out the activities of the immune system. They are able to specifically identify a foreign substance as being "non-self' or mutant cells and cause their destruction and elimination. There are two major classes of lymphocytes; B lymphocytes and T lymphocytes. There is also the natural killer cell that falls under the classification of lymphocytes.

a. B LYMPHOCYTES B cells are programmed to produce substances called antibodies also known as immunoglobulin. Each B cell produces a specific antibody for a specific antigen (foreign substance) much like a specific key is made for a specific lock. When an antibody locks with an antigen it essendally renders the antigen harmless and marks it for destruction. There are five classes of immunoglobulins; IgG, IgM, IgA, IgD, and IgE. Each has a different role in the immune defense scheme. IgG is the major immunoglobulin in blood. It coats microorganisms making them mom desirable for ingestion and destruction by other white blood cells. IgM is also found in the bloodstream and it is very effective in killing bacteria. IgA is found mainly in body fluids such as tears, saliva, respiratory and gastrointestinal secretions. Its function is seen as guarding the entrances into the body. These are the three immunoglobulins that are measurable in the peripheral blood. IgE and IgD are found in such small quantities in the blood stream and are not easily measurable. Elevated levels of immunoglobulins have been seen in persons infected with HIV. Why this occurs is not fully understood but is believed to be faulty regulation of the B cells.

Normal Values of Immunoglobulins: IgG: 650-1600mg/dl lgM: 50-320mg/dl IgA: 65-415mg/dl

b. T LYMPHOCYTES T cells do not produce antibodies but have a very major role in the immune response. They have two functions; (1)acting as regulators of the immune system and (2)directly attacking cells that are malignant or defective. There are two main types of T cells which vary in respect to their function. There is the T4 cells also called the "helper/inducer cells." These cells are essential for activating B cells, other T cells, natural killer cells and monocyte/macrophages when it detects that the body has been invaded by viruses, parasites and fungi. It is known that the HIV virus invades the T4 cell and renders the T4 cell ineffective in doing its normal functions. T8 cells are the other subset of T lymphocytes and are known as the "suppressor/cytotoxic" T cells. Their main function is to down regulate (turn-off) antibody production by the B cell and to suppress or turn off the cells once the infection is under control. The cytotoxic T cells kill cells that are infected by virus and also kill tumor cells.

NORMAL VALUES: T4 CELLS: 600-1200/cu.mm.; 60-40% T8 CELLS: 150-600/cu.mm.; 15-20%

3. Natural Killer Cells: NK Cells Natural killer cells are a type of lymphocyte that do not carry the markers to be B cells or T cells. Like cytotoxic T cells they attack and kill tumor cells and protect against a wide variety of infectious microbes. They are "natural" killers because they do not need additional stimulation or need to recognize a specific antigen in order to attack and kill. Persons with immunodeficiencies such as AIDS have a decrease in "natural" killer cell activity.

B. HIV STUDIES

1. HIV CULTURE/ CO-CULTURE

a. SYNCYTIA Syncytia is a test done for the presence of HIV in lymphocytes. Syncytia formation describes the characteristic cell fusion (sticking) pattem T4 cells show when infected with the virus. It is a way of measuring the destructive effect the virus has on lymphocytes. Syncytia formation is measured on a scale of 0-3+. SCALE: 0: negative, no syncytia seen 1+: questionable syncytia 2+: definite syncytia 3+: 1 or more seen per microscopic field

b. REVERSE TRANSCRIPTASE-RT Reverse transcriptese is an enzyme in HIV. This enzyme enables the virus to make a DNA copy of itself which can code for. the production of more virus. Measure the amount of reverse transcriptase in peripheral blood lymphocytes is one way of measuring HIV activity. The amount of the enzyme present is thought to be an indication of the amount of virus present in cells. It is presumed that a higher measurement of reverse transcriptase correlates with a larger amount of viral infection. >1000 = a positive culture

2. P24 ANTIGEN P24 is one the core proteins that makes up the structure of the virus. P24 found in the peripheral blood is thought to also correlate with the amount of virus in the peripheral blood. It is believed that there are measurable levels of P24 when first infected with the virus after which there is a strong antibody response to P24 in early disease. Low or unmeasurable levels of P24 may indicate that the virus is in a dormant stage. Spikes in P24 levels may indicate that HIV has begun active replication.

Measurements: >100 = (+)P24, activity occurring 50-100 = questionable activity <50 = back ground artifact

3. Beta-2 Microglobulin-B2M, BETA Beta-2 microglobulin (B2M) is a protein particle which is found on the surface of almost all cells including T4 cells. As cells die, the B2M is released in the blood. Elevated B2M level is seen in a number of diseases and chronic illnesses including HIV. As the level of B2M increases beyond the normal level it reflects a more rapid cell destruction. B2M is used to monitor the effects of treatment and disease state. B2M is an indirect measurement of HIV since B2M is found on many cells and can be elevated in other disease processes.

Levels. 0.9-3.0 MG/L is normal range.

4. OTHER TESTS

a. SKIN TEST-TETANUS TOXOID SKIN TEST One of the simplest ways of evaluating in-vivo (in the body) T cell immune response is through a delayed-type hypersensitivity skin test. For the development of a positive skin test there must be. previous exposure to the substance. If an individual has not received a tetanus shot in 3 years he/she may be given one during H/P. On the next visit a skin test is then given. This is done by administering a very small amount of tetanus toxoid just under the skin (intradermal injection) and producing a round, slightly raised area. In a normal immune system the response is a reddened hard spot which is measured in 24hrs. This is the response of T cells to the tetanus toxoid which it recognizes. Most persons with AIDS do not show a response due to the infection of T4 cells with the virus.

b. LAB STUDIES

TETANUS TOXOID-TT This is another test using tetanus toxoid to measure T cell response and is done in the lab using a sample of blood. In a healthy individual who has had tetanus immunization, the T cell will recognize the tetanus toxoid as foreign and proliferate (multiple). This proliferative activity is of value in determining a normal T cell immune response. Most people with HIV infection have a diminished proliferative response to tetanus toxoid.

PHA-Phytohemagglutinin PHA is a mitogen, a substance that is able to cause T cells to proliferate as well. It is used to measure non-specific response of T cells thus giving an indication of the "immune function" of the person's T cells.

III. SAFETY LABS

A. CBC/DIFFERENTIAL

1. WHITE BLOOD CELLS AND GRANULOCYTES Refer back to section II A.

2.PLATELETS NORMAL VALUE: M: 154,000-354,000/cu.mm. F: 162,000-380,000/cu.mm. Platelets are an active agent of inflammation when vascular damage occurs. They are not actually cells but fragments released by the megakaryocyte cell. Megakaryocyte is luge cell in the bone marrow whose functions is to produce platelets. When vascular damage occurs the platelets stick to -the vascular walls and themselves forming clots to prevent the loss of blood. Thus, it is important to have adequate numbers of normal functioning platelets to maintain hemostasis and effective coagulation of the blood. There are drugs which can potentially alter the platelet count making it necessary to monitor. Also, some people with HIV infection develop thrombocytopenia (less than 100,000/cc mm).

3. HEMOGLOBIN-Hgb NORMAL VALUE: M: 12.7-16.7g/dl F: 11.1-15.0g/dl Hemoglobin is the main component of red blood cells and is the essential protein that combines with and transports oxygen to the body cells for nourishment. It also collects carbon dioxide which is later released by the lungs. Any condition that results in a decrease in concentration of hemoglobin in the peripheral blood lowers the oxygen uptake and anemia results. Those who have a very low hemoglobin (less than 9.0) may require blood transfusions to help boost there, red blood cell count and hemoglobin levels.

4. HEMATOCRIT-Hct NORMAL VALUE: M: 36.7-48.3% F: 31.8-43.2 % Hematocrit measures the percentage of a given volume of whole blood that is occupied by red blood cells. Thus a hematocrit value of 40% indicates that 40ml of each 100ml of peripheral blood is composed of red blood cells. Measuring of the hematocrit and hemoglobin go hand in hand and when both are low treatment is usually required.

B. SMAC

1. LIVER FUNCTION TESTS The liver is a very complex organ having more than 500 functions. One of the many functions is filtering and cleaning the blood; removing impurities and harmful substances. It also breaks down old and worn out red blood cells and certain drugs that are taken in. Monitoring the SGOT, SGPT, total bilirubin and alkaline phosphatase is a way of determining how well the liver is functioning. Elevated levels indicate that there is impaired functioning of the liver. There are many factors that could cause impaired liver function: Hepatitis, Epstein-Barr Virus, Cytomegalovirus, bacteria, chemicals, drugs and even alcohol. Elevations in values correlates with the amount of damage that is occurring to the liver.

a. SGOT-Serum glutamic-oxaloacetic transaminase, AST NORMAL VALUES: 9-34u/l SGOT is an enzyme released by the Ever, heart muscle, skeletal muscle, pancreas and kidneys. A clinical diagnosis cannot be based on this lab value alone since several organs contain this enzyme.

b. SGPT-Serum glutamic-pyruvic transaminase, ALT NORMAL VALUES: 6-41u/l SGPT is an enzyme found in high concentrations in the liver and at lower concentrations in the heart, kidney and skeletal muscle. Both SGOT and SGPT are found in relatively low numbers in the peripheral blood. When elevations do occur in these enzymes it usually indicates that some tissue destruction is occurring.

c. TOTAL BILIRUBIN-T bili NORMAL VALUE: 0.1-1.5 mg/dl Bilirubin is from old or damaged red blood cells. Small amounts of bilirubin normally enter the bloodstream and circulate until they reach the liver and then into the bowel where bilirubin is further broke down and excreted.

d. ALKALINE PHOSPHATASE-Alk Phos NORMAL VALUE: 37-116u/I This is an enzyme found in bone, liver, kidney, intestine, and placenta. During bone formation or with liver and biliary tract disorders, serum levels will rise in proportion to the severity of the condition.

2. KIDNEY FUNCTION TESTS

a. CREATININE NORMAL VALUE: F: 0.7-1/3 mg/dl M: 0.9-1.6 mg/dl Serum creatinine value is used as a screening test of kidney (renal) function. Creatine is the metabolic end product of energy released from the skeletal muscle energy-storing compound, phosphocreatine. Creatine is removed from the blood stream by the kidneys and is excreted in the urine. The balance between production and excretion is indicated by the serum level and reflects kidney function. Elevations in serum creatine are equal to the degree of the kidneys' diminished function.

b. BLOOD UREA NITROGEN-BUN NORMAL VALUE: 8-22 mg/dl Blood urea nitrogen is most commonly used as a screening test of renal function. Urea is the chief end product of protein breakdown. It is formed in the liver and transferred by the blood to the kidneys for removal in the urine. Elevated BUN concentrations may result from inadequate kidney function causing a decrease in the rate of urea removal.

3. URINALYSIS

a. PROTEINURIA Protein in the urine, proteinuria, is a very sensitive indicator of kidney disorders. Measuring the amount of protein in the urine aids in diagnosis and directs therapy since the degree of proteinuria varies according to the type and severity of the disease. Transitory proteinuria unrelated to organic disease can occur following strenuous exercise or severe emotional stress. A 24-hour urine for protein measurement is the most accurate indicator of the severity of the condition and is done when protein has been detected in a urinalysis more than once

© 2005 LINQ Communications