Interleukin-12: potential clinical applications in the treatment and prevention of infectious diseases.

Interleukin-12 (IL-12) is a cytokine that promotes cell-mediated immunity by facilitating type 1 helper T-lymphocyte responses, enhancing the lytic activity of natural killer cells, augmenting specific cytolytic T-lymphocyte responses, and inducing the secretion of interferon-gamma. It can also boost the production of some subclasses of IgG antibodies. IL-12 has demonstrated activity in several mouse models of infectious diseases caused by viruses, protozoans, fungi, and mycobacteria. It has the potential for use either as a single immunotherapeutic agent, in combination with chemotherapeutic agents, or as a vaccine adjuvant. Endogenous IL-12 appears to play an important role in the host defence against intracellular pathogens; poor IL-12 production observed in mononuclear cells from patients infected with the human immunodeficiency virus may be involved in the susceptibility of this patient group to opportunistic infections. Clinical trials are being initiated to evaluate the possible therapeutic uses of IL-12.