Increased expression of proinflammatory cytokines in chronic lesions of human cutaneous leishmaniasis

The nature of the host cellular immune response largely determines the expression of disease following infection with the intracellular protozoans Leishmania spp. In experimental animals control and resolution of infection are mediated by gamma interferon and tumor necrosis factor alpha (TNF-α), whereas disease progression is associated with the production of interleukin 4 (IL-4), IL-5, IL-10, and transforming growth factor beta (TGF-β). We have analyzed the profile of cytokine gene expression directly in the lesions of 13 patients with localized cutaneous leishmaniasis due to Leishmania mexicana. All but one patient had a single lesion, and the time of evolution ranged from 8 days to 18 months. Cytokine gene expression was quantitated by reverse transcriptase PCR and interpolation from a standard curve. Gamma interferon, TNF-α, IL-1α, IL-6, IL-10, and TGF-β gene expression was present in all samples. IL-3 and IL-4 gene expression was barely detectable in 1 and 3 of 13 samples, respectively. IL-2 and IL-5 mRNAs were not found. A significant increase in the expression of IL-1α, TNF-α, IL-10, and TGF-β was observed in late lesions (≥4 months) compared with that in early lesions (≤2 months). Because of their inhibitory effects on macrophage function, the expression of IL-10 and TGF-β may play a role in the immunopathogenesis of chronic cutaneous leishmaniasis.