American cutaneous leishmaniasis: in situ characterization of the cellular immune response with time

The cellular nature of the infiltrate in the skin of patients with American cutaneous leishmaniasis was characterized by immunohistochemistry. The study population consisted of patients in Ceara, Brazil, an area where Leishmania braziliensis is endemic. Biopsies were taken from lesions present for 0.5-4 months duration and sections were stained with antibodies to T cells, T cell subsets, B cells, and macrophage markers to quantitate these cell types. The T cells accounted for 37.0 +/- 7.6% (mean +/- SD) of the infiltrate. The average percentages of CD4- and CD8-positive T cells were similar to each other, 20.4 +/- 9.0% and 19.9 +/- 6.7%, respectively. Interleukin-2 receptor-positive cells and B cells were infrequent, 3.7 +/- 3.0% and 2.3 +/- 3.1%, respectively. When the relationship between the age of the lesion at biopsy and the cellular phenotype was examined, it was noted that the percentage of positive cells remained fixed for all cell types except for that of gamma delta cells, which decreased with time. It is likely that gamma delta T cells are important in the early phase of the immune response to L. braziliensis and may, in general, be important in the early immune response of granulomatous diseases.