CD8(+) T Cells in Leishmania Infections: Friends or Foes?

Stäger, Simona; Rafati, Sima

Although CD8 + T cells positively correlate with cure of VL patients, one report suggested that these cells may contribute to the immunopathogenesis of PKDL (Ganguly et al., 2008) . Indeed patients suffering from PKDL showed a significant increase in the percentage of CD8 + T cells producing IL-10, which disappeared after cure (Ganguly et al., 2008) . IL-10-secreting CD8 + T cells are thought to play a regulatory role in different viral infection models. This CD8 + T cell subset was shown to display great cytotoxicity and produce granzyme B, IFN-γ, and TNF (Sun et al., 2009; Palmer et al., 2010; Trandem et al., 2011) . IL-10 + CD8 T cells seem to represent a transient and reversible state of CD8 + effector T cell differentiation. Its primary function is to balance pathogen clearance with bystander tissue damage (Zhang and Bevan, 2011) . Interestingly, in viral model, this subset disappears after the infection is cleared. Hence, it is possible that the IL-10-producing CD8 + T cells in PKDL patients are actually killing parasites and protecting patients from tissue damage, rather than suppressing protective responses. Further studies are needed in order to define the nature of these cells.