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)-γ 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-γ 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-γ production. Therefore, CD26 is not a surrogate marker for IFN-γ production in CL.