Differential interferon- gamma production characterizes the cytokine responses to Leishmania and Mycobacterium leprae antigens in concomitant mucocutaneous leishmaniasis and lepromatous leprosy.

Background: Tegumentary leishmaniasis and leprosy display similar spectra of disease phenotypes, which are dependent on cell-mediated immunity to specific antigens. Diffuse cutaneous leishmaniasis and lepromatous leprosy represent the anergic end of the spectrum, whereas mucocutaneous leishmaniasis and tuberculoid leprosy are associated with marked antigen-specific cellular immune response.

Methods: We characterized and compared the cell-mediated response to Leishmania and Mycobacterium leprae antigens in a patient with an intriguing association of mucocutaneous leishmaniasis with lepromatous leprosy, which are at opposite ends of the immunopathological spectra of these diseases. This was done by performance of skin tests and by assessment of the cell proliferation and cytokine production of peripheral blood mononuclear cells (PBMCs).

Results: Strong skin-test reactions and PBMC proliferation were observed in response to Leishmania antigens but not to M. leprae antigens. The stimulation of PBMCs with Leishmania and M. leprae antigens induced comparable levels of tumor necrosis factor- alpha , interleukin-5, and interleukin-10. However, the interferon- gamma response to Leishmania antigens was remarkably high, and that to M. leprae antigens was almost nil.

Conclusions: We found that concomitant leprosy and tegumentary leishmaniasis can produce opposite polar forms associated, respectively, with absent or exaggerated cell-mediated immune responses to each pathogen. This suggests that independent mechanisms influence the clinical outcome of each infection. Moreover, interferon- gamma appears to play a major role in the clinical expression of these intracellular infections.