Regulation of interleukin-12 production in antigen-presenting cells.

Interleukin-12 is a cytokine produced by antigen-presenting cells that is essential for host defense against intracellular microbial infection and control of malignancy by virtue of its ability to stimulate both innate and adaptive immune effector cells. The immune potentiating capacity of IL-12 and its mandatory requirement in host defense predispose it to rigorous regulation. The time, localization, and magnitude of IL-12 production during an immune response strongly influence the type, extent, and, ultimately, the fate of the response. Disturbance of this evolutionarily maintained "balance of power" frequently leads to immunologic disorders. This article reviews the intricate pathways that have been uncovered in which IL-12 production is modulated by numerous pathogens and immunological regulators. The understanding of IL-12 regulation in physiological settings will undoubtedly lend valuable support to the design of therapeutic applications of IL-12.