Few studies have been conducted with human VL patients. However, most of the studies ascribe a protective role for CD8 + T cells, in agreement with results obtained from experimental models. Indeed, the control of L. infantum infection was shown not only to be associated with IFN-γ-producing CD4 + T cells, but also with CD8 + T cells (Mary et al., 1999) . Interestingly, during active VL, CD8 + T cells are less responsive to stimulation and a greater percentage stains positive for Annexin V compared to healthy controls (Clarencio et al., 2009 ). These observations correlate very well with what we observed in mice experimentally infected with L. donovani, where CD8 + T cells became increasingly dysfunctional during chronic infection and died by exhaustion (Joshi et al., 2009) . Whether human CD8 + T cells also display signs of exhaustion during active VL still remains to be tested.