Indirect evidence of the role of NK cells to the protective immune response against Leishmania come from the observation that, in individuals with SC infection as well as individuals without exposure to Leishmania, NK cells is the main source of IFN-γ upon stimulation in vitro with L. aethiopica (Maasho et al., 1998; Nylen et al., 2003). This evidence concerns the gene IFNG and infection.