Although initial studies have identified IL-27 as an inflammatory cytokine since it can promote Th1 responses by enhancing T-bet expression in CD4+ T cells, later reports have shown that IL-27 can down-regulate T cell activity both, dependent and independent of IL-10 demonstrated in human visceral leishmaniasis (Hunter et al., 1994; Ansari et al., 2011). This evidence concerns the gene IL27 and visceral leishmaniasis.