Interleukin-12: a proinflammatory cytokine with immunoregulatory functions that bridge innate resistance and antigen-specific adaptive immunity.
Interleukin-12 (IL-12) is a heterodimeric cytokine produced mostly by phagocytic cells in response to bacteria, bacterial products, and intracellular parasites, and to some degree by B lymphocytes. IL-12 induces cytokine production, primarily of IFN-gamma, from NK and T cells, acts as a growth factor for activated NK and T cells, enhances the cytotoxic activity of NK cells, and favors cytotoxic T lymphocyte generation. In vivo IL-12 acts primarily at three stages during the innate resistance/adaptive immune response to infection: 1. Early in the infection, IL-12 is produced and induces production from NK and T cells of IFN-gamma, which contributes to phagocytic cell activation and inflammation; 2. IL-12 and IL-12-induced IFN-gamma favor Th1 cell differentiation by priming CD4+ T cells for high IFN-gamma production; and 3. IL-12 contributes to optimal IFN-gamma production and to proliferation of differentiated Th1 cells in response to antigen. The early preference expressed in the immune response depends on the balance between IL-12, which favors Th1 responses, and IL-4, which favors Th2 responses. Thus, IL-12 represents a functional bridge between the early nonspecific innate resistance and the subsequent antigen-specific adaptive immunity.
Trinchieri
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Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104-4268, USA.
D000222:Adaptation, Physiological; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D003141:Communicable Diseases / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D006801:Humans; D007249:Inflammation / Q000209:etiology; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000276:immunology; D051379:Mice; D009369:Neoplasms / Q000276:immunology; D010586:Phagocytes / Q000276:immunology; D018123:Receptors, Interleukin / Q000276:immunology; D053707:Receptors, Interleukin-12; D013601:T-Lymphocytes / Q000276:immunology
D016207:Cytokines; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D018664:Interleukin-12