The Histopathological Changes and Immunohistochemical Findings of Acute, Chronic Nonlupoid and Chronic Lupoid Types of Cutaneous Leishmaniasis

Dry type localized cutaneous Leishmaniasis due to Leishmania tropica is one of the most prevalent cutaneous parasitic infections in Kerman province. It seems that cellular immune response and the nature of immune inflammatory cells comprising the inflammatory background play a determinant role in this infection. Skin biopsies of 53 patients with acute(<2 years duration), nonlupoid chronic(≥2 years duration) and lupoid chronic (new lesions around old scar) types of cutaneous leishmaniasis due to Leishmania tropica were studied by hematoxylin-eosin staining for evaluation of inflammatory cells and epidermal and dermal changes. Immunohistochemical staining was used to determine immunophenotypic patterns (CD1a, CD68, CD3, CD8, CD4, CD20) and to evaluate host immune response at tissue level, the correlation between the presence and concentration of certain cell types, and the clinical presentation and duration of disease. Mean percentages of epidermal and dermal Langerhans cells CD1a+ were higher in lupoid than in acute lesions. Also, the predominant T lymphocyte in acute, chronic and lupoid leishmaniasis was T CD8+. It seems that Langerhans cells CD1a+ are responsible for the suppression of the inflammatory response against L.tropica infection and by providing Leishmania antigens in a steady state induce tolerance to the Leishmania antigens and consequently cause cutaneous chronic lupoid leishmaniasis. This study also suggests that T CD8+ play an effective role in parasite elimination and in the process of healing of cutaneous leishmaniasis due to Leishmania tropica.