CD26 expression on CD4+T cells in patients with cutaneous leishmaniasis.

Surrogate marker(s) of protection in human leishmaniasis is not well defined. In this study, T helper 1 (Th1) and Th2 cytokine profiles and CD26 expression on CD4(+) T cells in peripheral blood mononuclear cells of patients with healing or non-healing forms of cutaneous leishmaniasis (CL) stimulated with Leishmania antigens were assessed. The level of interferon (IFN)-gamma production was significantly higher in patients with healing or non-healing forms of CL than in healthy controls, but it was not significantly different between the two patient groups. The level of interleukin-5 production was significantly higher in patients with the non-healing form of CL than in the two other groups. There was a significant increase in the level of CD26 expression on CD4(+) T cells in patients with healing (P < 0.001) or non-healing (P = 0.025) forms of CL compared with the control group, but no significant difference was seen between the two patient groups. A weak positive correlation was seen between IFN-gamma production and CD26 expression on CD4(+) T cells of patients with the healing form of lesion (r = 0.54, P = 0.008), but this correlation was not observed in patients with the non-healing form of CL (r = 0.53, P = 0.078). Surface CD26 is not correlated with the clinical manifestation of CL or IFN-gamma production. Therefore, CD26 is not a surrogate marker for IFN-gamma production in CL.