Another study also showed that CD8 + T cells purified from L. infantum-infected mice expressed IFN-γ and TNF, and displayed considerable cytotoxic activity against cells expressing Leishmania antigens (Tsagozis et al., 2003) . Interestingly, killing of infected target cells was mediated by both the perforin and Fas/FasL pathways (Tsagozis et al., 2003) . The Fas/FasL pathway has also been implicated in the defense against L. donovani (Alexander et al., 2001) . Indeed, gld and lpr mice, which lack a functional Fas/FasL pathway, were shown to be more susceptible to L. donovani.