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, plasmacytoid dendritic cells, microglia, and (CD38- CD44 +) B cells. IL-12 is 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 helper 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 cytokines by peripheral blood T cells 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 a disulfide bond, 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 can bind the IL-12 receptor thereby acting as an IL-12 antagonist. In addition, the p40 subunit is expressed more than 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 patients with multiple sclerosis. Elevated levels of IL-12 have also been reported in autoimmune diseases and 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 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.
Important Note
The measurement of Interleukin 12p70 (IL-12p70) is only performed for research purposes in the context of clinical studies and experimental protocols.
