The discrepancy between the findings in the low-and the highparasite dose model was clarified by another work that compared the requirements of CD8 + T cells in both systems (Uzonna et al., 2004) . Interestingly, in the low infection model CD8 + T cells producing IFN-γ were essential for modulating CD4 + T cell responses toward a Th1 response. In contrast, C57BL/6 mice inoculated with a high L. major dose did not require CD8 + T cell help to generate protective Th1 responses. The CD8 + T cell requirement for optimal IFN-γ production by Th1 cells was also proposed in a high-dose L. major infection model in BALB/c mice (Herath et al., 2003) . Moreover, CD8 + T cell-derived IFN-γ was reported to contribute to the induction of nitric oxide production in macrophages during experimental cutaneous leishmaniasis (Stefani et al., 1994) .