IN-SITU EXPRESSION OF INTERLEUKIN-10 AND INTERLEUKIN-12 IN ACTIVE HUMAN CUTANEOUS LEISHMANIASIS

Th1-type cellular immune responses (interferon-gamma) play a critical role in protection against Leishmania spp. infection, whereas Th2-type cytokines (interleukin (IL)-4, IL-IO) have a counter-protective effec t. IL-12, a potent inducer of Th1-type cellular immune responses, may play a pivotal role in the development of a protective response. We fo und that IL-IO and IL-12 mRNAs were expressed in most lesions of indiv iduals with active cutaneous leishmaniasis. The quantity of IL-12 mRNA was highly variable but correlated strongly with the level of interfe ron-gamma expression. IL-12 expression also paralleled the expression of IL-10, a potent in vitro suppressor of IL-12 and interferon-gamma p roduction. The more chronic, non-healing lesions generally had higher levels of IL-12 mRNA indicating that the expression of this cytokine a lone was not sufficient to induce healing. Although the in situ produc tion of IL-10 did not appear to block IL-12 expression, IL-10 may stil l promote disease by direct suppression of macrophage activation.