IL10 and visceral leishmaniasis: While IL-10 plays an important role in down regulating Th1 immune response, decreasing lymphocyte proliferation and production of IFN-γ in patients with visceral leishmaniasis (Carvalho et al., 1994a; Nylen and Sacks, 2007), the role of IL-10 in the pathogenesis of TL is not so clear.