Immunocytochemical and histopathologic characterization of lesions from patients with localized cutaneous leishmaniasis caused by Leishmania panamensis.

Localized cutaneous leishmaniasis (LCL) in Colombia is caused primarily by Leishmania panamensis, a different species from those reported in Brazil, French Guiana, and Venezuela. Because different parasites may elicit disparate immune responses, the present study was undertaken to establish the leukocyte participation in the immune response against L. panamensis. Epidermal and dermal immune complexes were studied using an avidinbiotin immunoperoxidase technique and specific monoclonal antibodies. In LCL, the epidermis showed keratinocytes expressing intercellular adhesion molecule-1, a universal expression of human leukocyte antigen-DR, and a hyperplasia of CD1a+ Langerhans cells. The dermal granuloma observed had a mean +/- SEM value for the CD4/CD8 ratio of 0.80 +/- 0.06. The expression of the activation molecules CD25 (interleukin-2 receptor) and CD18 (lymphocyte function-associated antigen-1 beta), 10.5% and 38.1% respectively, suggests that many cells are primed and proliferating. Most T cells in the granuloma expressed alpha beta T cell receptor (TCR) (40.3%) whereas only a few (6.7%) expressed gamma delta TCR. The results show that Colombian LCL patients possessed the appropiate activation and accessory signals from immunocompetent cells to trigger the effector phase of the immune response and eventually eliminate the parasite.