Interleukin (IL)-13 is the predominant th2 cytokine in localized cutaneousleishmaniasis lesions and renders specific CD4(+) T cells unresponsive to IL-12

Semiquantitative reverse transcription-polymerase chain reaction analysis o f leishmania lesion cytokine profile showed a Th2 cytokine expression patte rn, as reflected by interleukin (IL)-4 and IL-13 mRNA expression. There was a predominance of IL-13 in most lesions from patients with American locali zed cutaneous leishmaniasis caused by Leishmania guyanensis. IL-13 producti on by peripheral blood mononuclear cells in response to specific leishmania antigens was confirmed in these patients. The absence of the second chain of the IL-12 receptor (IL-12R beta2) mRNA expression in lesions and the pre sence of specific IgE and IgG4 in some serum samples demonstrated the funct ional role of these Th2 cytokines. IL-13, unlike IL-4, rendered specific T cells unresponsive to IL-12 by inhibiting the expression of the IL-12R beta 2 chain. These data establish the crucial role of IL-13 in human cutaneous leishmaniasis.