Immunologic determinants of disease evolution in localized cutaneous leishmaniasis due to Leishmania major

Localized cutaneous leishmaniasis caused by Leishmania major is polymorphic in its clinical presentation and evolution. Clinical and parasitologic features and disease evolution of 112 Tunisian patients was evaluated. The expression of interleukin (IL)-4, IL-6, IL-10, IL-12 (p40), interferon (IFN)-γ, and tumor necrosis factor (TNF)-α mRNA was analyzed by reverse transcription-polymerase chain reaction in 73 biopsies. Cytokine mRNA expression varied individually over a wide range; TNF-α, IL-6, and IFN-γ were detectable in >90% of lesions, IL-12 and IL-10 in 40% and 70%, respectively, and IL-4 in only 9%. Statistical analysis demonstrated positive association between the level of IL-12 and IFN-γ and the presence of parasites in the lesions. Unfavorable evolution of the lesions was positively associated with high IL-10, IL-12, and IFN-γ mRNA expression. These results indicate that an unfavorable clinical outcome was not related to an inadequate Th1 cell response and suggest that the macrophage-activating effect of IFN-γ may be inhibited by the concomitant expression of IL-10.