Interleukin 12 (IL-12) is a pleiotropic cytokine formerly called a cytotoxic lymphocyte maturation factor (CLMF) or natural killer cell stimulating factor (NKSF) and is mainly produced by macrophages. In addition to macrophages, IL-12 also produces dendritic cells, monocytes, Langerhans cells, neutrophils, keratinocytes, plasma cell dendrites, microglia, and (CD38- CD44 +) B cells. IL-12 has been shown to be a pro-inflammatory cytokine produced by phagocytes, B-cells and other antigen-presenting cells that modulate immune responses by favoring the generation of type 1 T-cells (Th1).
IL-12 exerts a variety of biological effects on T cells and natural killer (NK) cells. In addition to promoting Th1 growth and its ability to promote cytolytic activity, it mediates some of its physiological activities by acting as a potent inducer of IFN-γ production and stimulation of other peripheral T-cells by its peripheral T-cells, blood and NK cells. IFN-γ then enhances the ability of phagocytes to produce IL-12 and other proinflammatory cytokines. Thus, IFN-γ induced by IL-12 acts in a positive feedback loop, which represents an important proliferative mechanism in the inflammatory response to infections.
The role of IL-12 in the development of a Th1 type of immune response from undifferentiated T-cells demonstrates its critical role in modulating the immune response and may be useful in the treatment of cancer.
IL-12 is a heterodimeric cytokine, consisting of a 35 kDa light chain (p35) and a 40 kDa heavy chain (p40) linked by disulfide, resulting in the formation of the biologically active form of IL-12 with a molecular weight of 70 kDa (p70). The p40 subunit can also form a homodimer, which has been shown to be able to bind the IL-12 receptor thereby acting as an IL-12 antagonist. In addition, the p40 subunit has been found to be expressed in excess of p70.
The critical role of IL-12 in various pathological conditions has been demonstrated. Elevated plasma levels have been found in neurological disorders. Significant increases were measured in autistic patients and in patients with multiple sclerosis. Elevated levels of IL-12 have also been reported in autoimmune diseases and in chronic inflammatory reactions, such as in the synovial fluid of patients with osteoarthritis, rheumatoid arthritis and seronegative spondyloarthropathy, in patients with Sjogren's syndrome and atherosclerosis. Changes in IL-12 levels have been reported in a large number of both bacterial and viral infections, obstructive jaundice, septic shock, mycobacterial tuberculosis, and HIV infection. Interleukin 12 also plays a critical role in allograft rejection and inflammatory skin lesions.
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.
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