T Cells Specific to Leishmania and Other Nonrelated Microbial Antigens Can Migrate to Human Leishmaniasis Skin Lesions

Abstract

Immunopathological studies have contributed to the characterization of in situ inflammatory infiltrates in cutaneous leishmaniasis (CL). However, little is known about the T-cell antigen reactivity of these lesions. Our objective was to analyze the responsiveness of lymphocytes from CL lesions to leishmanial and nonrelated antigens in terms of proliferation and the production of cytokines. Mononuclear cells were extracted from lesions, and blood from CL patients infected with Leishmania (Viannia) braziliensis. Activated cells accounted for 35-45% of lesions T-cell subsets. Elevated levels of C1.7/CD244(+)CD8(+) T cells suggest in situ cytotoxic effector function. Lymphocytes isolated from the leishmaniasis lesions proliferated and produced IFN-gamma in response to leishmanial antigens as well as to irrelevant antigens such as Toxoplasma gondii (Tg). Patients presenting with larger lesions had the highest lymphocyte proliferation indexes. A high frequency of Tg-specific cells was detected in the lesions by limiting dilution assay, similar to the frequency of Leishmania-specific cells. Importantly, Tg-reactive cells were not found in lesions of patients without a history of toxoplasmosis. The proportion of Leishmania-reactive CD4(+) and CD8(+) T cells in the lesions was quite variable. Overall, these data suggest that T cells reactive to nonrelevant antigens can migrate to leishmanial lesions and possibly influence the pathogenesis of the disease.

CD3+CD4negCD8neg (double negative) T lymphocytes and NKT cells as the main cytotoxic-related-CD107a+ cells in lesions of cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis

“…Flow cytometry (FCM) has been extensively applied as a key method to address these issues, and the majority of the reports are based on peripheral-blood-sample analysis [6, 11, 28–30]. However, it is known that lymphocytes are recruited from blood to lymph nodes, primed with antigens and then migrate to lesion sites; consequently, frequencies of antigen-specific T cells are higher in leishmaniasis lesions than in blood [7, 17, 31, 32].…”

Assessment of Interferon-γ Levels and Leishmanin Skin Test Results in Persons Recovered for Leishmaniasis

“…However, production of IFN-γ by unrelated T cells stimulated with leishmanial antigens has been reported. 30 Pre-exposure to organisms with cross-reacting antigens (i.e., Mycobacteria spp.) might also be cause of the IFN-γ response.…”

CD8+ T cells in cutaneous leishmaniasis: the good, the bad, and the ugly

“…Thus, it may not be surprising that CD8 + T cells isolated from leishmanial lesions of L. braziliensis patients who were seropositive for Toxoplasma contained both leishmanial- and Toxoplasma -specific T cells (80). However, the role that potentially large numbers of bystander T cells play in modulating disease, if any, is unclear.…”