Resolving lesions in human cutaneous leishmaniasis predominantly harbour chemokine receptor CXCR3-positive T helper 1/T cytotoxic type 1 cells.

BACKGROUND

Cutaneous leishmaniasis (CL) is an epidemic disease affecting millions of individuals worldwide. Treatment options have several side-effects and a vaccine does not exist at present.

OBJECTIVES

To translate information about protection against CL from mice to man, we studied the local immune response in CL skin biopsies and correlated these findings with clinical information.

METHODS

The frequency of inflammatory cells was determined in skin biopsies of 20 patients diagnosed with CL using immunohistochemistry. In addition, the nature of the resulting adaptive immune response was assessed by (double) immunostaining against CD4 and chemokine receptors CXCR3 (T helper 1, Th1)/CCR4 (Th2).

RESULTS

All lesions contained CD4+ and CD8+ T cells, B cells and CD68+ macrophages. CD1a+ epidermal Langerhans cells were absent above the centre of the lesions, but normally distributed in the surrounding tissue. Mast cell and CD56+ natural killer cell numbers were not affected. Interestingly, CCR4+ Th2 cells were not detected in any of the 20 samples. In contrast, the number of infiltrating CXCR3+ cells was high and the majority of these were CD4+ or CD8+ indicating that they represent interferon-gamma-producing Th1/T cytotoxic type 1 (Tc1) cells. Finally, these findings did not correlate with clinical information about the country where the infection was acquired, or age or sex of the patients. However, lesions that had already persisted for more than 6 months contained fewer CXCR3+ CD4 and CD8 T cells than those that had persisted for less than 6 months.

CONCLUSIONS

Our data on the inflammatory infiltrate of human CL lesions underline the relevance of findings obtained in experimental models. Both Th1 and Tc1 cells appear to be critical for healing in CL in mouse and man.