Monocyte derived IL 10 and PGE2 are associated with the absence of Th 1 cells and in vitro T cell suppression in lepromatous leprosy.

Our previous studies had shown that the clinicopathological spectrum in leprosy was associated with discrete T cell subsets in circulation, with tuberculoid patients having antigen-induced Th 1, whereas lepromatous leprosy patients with antigen-specific T cell anergy possessed Th 2 cells. The present study shows that infected monocytes from lepromatous but not tuberculoid leprosy patients released soluble factors (MoF(s)) containing IL-10 and PGE2 which inhibited M. leprae induced in vitro lymphoproliferation of previously sensitised healthy or tuberculoid leprosy subjects. A strong negative correlation was observed between adherent cell derived IL-10 and IL-2 at the level of both the product and cytokine mRNA. Moreover, anti-IL-10 antibodies and indomethacin partially reversed the suppressor effects of MoF(s). Taken together these studies indicate that infected monocytes contribute to the development of T cell anergy by releasing factors that affect regulatory cytokines and T cell subset differentiation in lepromatous leprosy.