In addition to killing and releasing cytokines and chemokines, recent studies have ascribed a novel regulatory role for CD8 + T cells (Sun et al., 2009; Palmer et al., 2010; Trandem et al., 2011) . Regulatory CD8 + T cells represent a transient state of effector CD8 + T cells (Trandem et al., 2011) , which is possibly induced by potent TCR stimulation, which promotes the production of the immunosuppressive cytokine IL-10 (Zhang and Bevan, 2011) . Not only do these cells produce IL-10, but they are also excellent killers and produce normal to higher amounts of IFN-γ and TNF (Sun et al., 2009; Palmer et al., 2010; Trandem et al., 2011) . The main function of these cells is thought to lie in the prevention of immunopathology during infection without affecting the kinetics of pathogen clearance. IL-10-producing CD8 + T cells have also been observed in human patients infected with L. guyanensis (Bourreau et al., 2007) and in patients suffering from post-kalaazar dermal leishmaniasis (PKDL; Ganguly et al., 2008) . The role of regulatory CD8 + T cells in the immune response against parasitic infections is still unknown.