Interleukins | IL-12

Interleukin-12 (IL-12) is a heterodimeric cytokine with broad immunoregulatory properties that belongs to a larger family of proteins, termed the IL-12 related cytokines. The IL-12 related cytokines are generated from five independently regulated genes that homodimerize and heterodimerize to form seven secreted family members. These proteins have overlapping as well as distinct biologic properties and this article focuses specifically on IL-12, p80, and p40. IL-12, a disulfide-linked heterodimer composed of a p40 and p35 subunit, has been identified as an immune cell stimulator that promotes differentiation and proliferation of T cells and enhances the production of interferon gamma. Human studies and murine experimental models have implicated IL-12 in the regulation of multiple immunologic processes including regulation of CD4+ and CD8+ T-cell differentiation, host defense, autoimmunity, tumor cell immune recognition, alloimmunity, and host response to vaccine administration. p80 is a disulfide-linked p40 homodimer that can function as a competitive antagonist of IL-12 and a macrophage chemoattractant. Specific topics discussed in this article include the structure, regulation, function, receptor utilization, and role of IL-12 related cytokines in respiratory disease.