T cell-monocyte contact enhances tumor necrosis factor-alpha production inresponse to Mycobacterium leprae

Tumor necrosis factor (TNF)-alpha has been implicated as a key factor in in flammatory processes occurring in erythema nodosum leprosum (ENL), In the p resent study, the roles of soluble factors and contact-mediated interaction in the induction of enhanced TNF-alpha secretion in leprosy have been inve stigated. In vitro studies have demonstrated that Mycobacterium leprae per se is a poor stimulus for TNF-alpha production by purified monocytes obtain ed from normal subjects, although this could be enhanced by either exogenou s interferon-gamma or cell contact with fixed activated T lymphocytes, Furt her investigations demonstrated that monocyte-T cell contact enhanced M. le pra-induced TNF-alpha production by peripheral blood mononuclear cells of E NL patients and was modulated by blocking antibodies to CD40L, CD69, and CD 18, These results suggest that physical contact with T cells isolated from patients in a particular disease state (ENL) modulates monocyte function an d may contribute to the secretion of proinflammatory cytokines described in ENL.