Cell populations in lesions of cutaneous leishmaniasis of Leishmania (L.) amazonensis-infected rhesus macaques, Macaca mulatta

The cellular nature of the infilrate in cutaneous lesion of rhesus monkeys experimentally infected with Leishmania (L.) amazonensis was characterized by immunohistochemistry. Skin biopsies from infected animals with active or healing lesions were com pared to non-infected controls (three of each type) to quantitate inflammat ory, cell types. Inflammatory cells (composed of a mixture of T lymphocyte subpopulations, macrophages and a small number of natural killer cells and granulocytes) were more numerous in active lesions than in healing ones. T- cells accounted for 44. 7 +/- 13.1% of the infiltrate in active lesions (ve rsus CD2+ = 40.3 +/- 5. 7% in healing lesions) and T-cell ratios favor CD8 cells in both lesion types. The percentage of cells expressing class II an tigen (HLA-DR+) in active lesions (95 +/- 7.1%) was significantly, higher ( P < 0.005)from the healing lesions (41.7 +/- 12.7%). Moreover, the expressi on of the activation molecules CD25 (congruent to 16%), the receptor for in terleukin-2, suggests that many T cells are primed and proliferating in act ive lesions. Distinct histopathological patterns were observed in lesions a t biopsy: but healing lesions contained more organised epithelioid granulom as and activated macrophages, followed by fibrotic substitution. The progre ssion and resolution of skin lesions appears to be very similar to that obs erved in humans, confirming the potential for this to be used as a viable m odel to study the immune response in human cutaneous leishmaniasis.