Interleukin-12: a proinflammatory cytokine with immunoregulatory functions that bridge innate resistance and antigen-specific adaptive immunity

Annu Rev Immunol. 1995;13:251-76. doi: 10.1146/annurev.iy.13.040195.001343.


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.

Publication types

  • Review

MeSH terms

  • Adaptation, Physiological
  • Animals
  • B-Lymphocytes / immunology
  • Communicable Diseases / immunology
  • Cytokines / biosynthesis
  • Humans
  • Inflammation / etiology
  • Interleukin-12 / genetics
  • Interleukin-12 / immunology*
  • Interleukin-12 / pharmacology
  • Killer Cells, Natural / immunology
  • Mice
  • Neoplasms / immunology
  • Phagocytes / immunology
  • Receptors, Interleukin / immunology
  • Receptors, Interleukin-12
  • T-Lymphocytes / immunology


  • Cytokines
  • Receptors, Interleukin
  • Receptors, Interleukin-12
  • Interleukin-12