In Leishmaniasis, the CD40-CD40L signaling has been proposed to regulate secretion of two counter regulatory cytokines, IL-12 and IL-10 via the p38 MAPK and ERK pathway, by skewing the CD40 signaling towards ERK 1/2, which then induces IL-10; in turn, the increased IL-10 prevents CD40 induced p38 MAPK activation, translating into a reduction in IL-12 [4], [40]. This evidence concerns the gene CD40 and leishmaniasis.