The immune system consists of two subsystems: the humoral immune system and the cellular immune system. The primary cell of humoral immunity is B-cell, which matures in the bone marrow.
B lymphocytes circulate in the blood in an inactive state. When B lymphocytes are exposed to a particular protein or microorganisms (antigens) for the first time, they produce antibodies (immunoglobulins) that bind to the antigen. This production of antibodies can take weeks or even years, but antibodies are usually detectable in the blood within 6 months. In subsequent exposures to the same antigen, the antibodies of which are already present in the blood, the response appears almost immediately.
T-cells, which mature in the thymus, include the cellular immune system. When a T lymphocyte encounters a particular protein or microorganism (antigen) to which it is programmed to respond, it can directly attack and destroy the antigen. There are several types of T lymphocytes. Cytotoxic T cells release toxic chemicals that directly destroy the antigen. T helper cells, which have the CD4 marker, stimulate the response of all other T lymphocytes. They can also stimulate the humoral immune response. Suppressor T cells, which have the CD8 marker, are responsible for the abolition of both humoral and cell mediated immune responses, when needed. Memory cells can "remember" antigens they had previously encountered. These cells are therefore responsible for the immediate response to the antigen when treated a second time.
T- and B-lymphocyte screening is performed to evaluate the status of the immune system. Usually T- and B-lymphocyte counts are performed to evaluate the status of the immune system in patients infected with the human immunodeficiency virus (HIV). As helper T cells (CD4) become infected with HIV, their numbers decrease. Thus, as the number of CD4 cells decreases, the dominant cells become suppressor T lymphocytes, keeping the immune system suppressed and unable to fight infections.
What Do Pathological Values Mean?
- T Lymphocyte Increase: Graves' Disease.
- T Lymphocyte Decrease: Acute viral infection, DeGeorge syndrome, HIV infection, Hodgkin's disease, increased risk for AIDS, increased risk for occasional infections, malignancies, Nezelof syndrome, Wiskott-Aldrich syndrome
- B Lymphocyte Increase: Chronic lymphocytic leukemia, systemic lupus erythematosus.
- B Lymphocyte Decrease: Deficiency of IgG, IgA, IgM, Hypogammaglobulinemia, lymphomas, multiple myeloma, nephrotic syndrome
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.