IMMUNOCYTOCHEMICAL AND HISTOPATHOLOGIC CHARACTERIZATION OF LESIONS FROM PATIENTS WITH LOCALIZED CUTANEOUS LEISHMANIASIS CAUSED BY LEISHMANIA-PANAMENSIS

Localized cutaneous leishmaniasis (LCL) in Colombia is caused primaril y 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 t o establish the leukocyte participation in the immune response against L. panamensis. Epidermal and dermal immune complexes were studied usi ng an avidinbiotin immunoperoxidase technique and specific monoclonal antibodies. In LCL, the epidermis showed keratinocytes expressing inte rcellular adhesion molecule-1, a universal expression of human leukocy te 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 (interl eukin-2 receptor) and CD18 (lymphocyte function-associated antigen-1 b eta), 10.5% and 38.1% respectively, suggests that many cells are prime d and proliferating. Most T cells in the granuloma expressed alpha bet a T cell receptor (TCR) (40.3%) whereas only a few (6.7%) expressed ga mma delta TCR. The results show that Colombian LCL patients possessed the appropiate activation and accessory signals from immunocompetent c ells to trigger the effector phase of the immune response and eventual ly eliminate the parasite.