Because FACS- and PCR-based analyses examine T-cell clonality from different aspects, the future development of tetramer-based FACS on Leishmania Ag-specific CD4+ T cells would be helpful for accurate assessment.

Nevertheless, results from these studies clearly indicate the magnitude of CD4+ T-cell activation induced by different Leishmania species correlates with infection outcome. Having demonstrated strong T-cell activation and IFN-γ production in Lb infection, we then examined whether pre-infection with Lb could provide cross-protection against secondary La infection via an enhanced T-cell activation. We showed that this cross-protection correlated nicely with the increased T-cell activation and IFN-γ production from CD4+ T cells (Figure 3), a finding consistent with previous studies on L. major Selumetinib pre-infection followed with a secondary infection with La or L. mexicana parasites (24,32). Again, the tested 4 Vβ subset contributed selleck compound comparably to IFN-γ production. Because the quality or multifunctional

capacity of CD4+ T cells is a crucial determinant in vaccine-mediated protection against L. major (33) and malaria (34), we investigated the production of several cytokines from CD4+ CD44+ effector T cells in La- or Lb-infected mice. It was evident that CD4+ CD44+ T cells derived from Lb-infected mice tended to produce high levels of IFN-γ, but low levels of IL-10 and IL-17 (Figure 5a), and that this Th1-favoured response was maintained even when cells were stimulated in vitro with La antigen (Figure 5b). Therefore, the healing from from control of Leishmania infection requires sequential events that include efficient dendritic cell activation (5), adequate innate responses (12) and activated Th1-type responses to a relatively broad spectrum of parasite antigens. Notably, the adoptive

transfer of Lb-specific CD4+ T cells into naïve mice failed to protect mice against the subsequent La infection (data not shown), a finding consistent with a previous report showing the lack of protection against L. mexicana infection following the adoptive transfer of L. major-specific CD3+ T cells (24). The reasons for this lack of cross-protection by cell transfer alone may include the maintenance of effective Th1 responses and cell recruitment in the recipients, as well as the unique features of L. amazonensis and L. mexicana parasites (35). In summary, our comparative analyses of CD4+ T cells in different models of cutaneous leishmaniasis indicate that Leishmania infection does not change the diversity of the TCR Vβ repertoire in either self-healing or nonhealing model and that multiple TCR Vβ CD4+ T cells contribute collectively and comparably to IFN-γ production.