Interleukin-12 secretion by Mycobacterium tuberculosis-infected macrophages.

Infection with Mycobacterium tuberculosis or phagocytosis of large latex beads induced interleukin-12 (IL-12) production in macrophages. In contrast, tumor necrosis factor (TNF) was produced only in response to M. tuberculosis infection, not after phagocytosis of latex beads. Comparable results were obtained with cells from immunocompetent C57BL/6 and gamma interferon receptor-deficient mutant mice. Thus, phagocytosis by mechanisms not specific for M. tuberculosis was a sufficient trigger for IL-12 secretion, emphasizing the central role of this cytokine in the initiation of anti-infective immunity.