The cytokine profile produced by peripheral blood mononuclear cells (PBMC) in response to leishmania antigens and the ability of interleukin-10 (IL-10) and transforming growth factor ␤ (TGF-␤) to modulate the immune response were evaluated in 21 mucosal leishmaniasis patients. Patients with mucosal disease exhibited increased gamma interferon (IFN-␥) and tumor necrosis factor alpha (TNF-␣) secretion and decreased IL-10 secretion compared to patients with classical cutaneous leishmaniasis. CD4 ؉ Th1 cells were the main source of IFN-␥ and TNF-␣ production in mucosal leishmaniasis patients. Evaluation of cytokine gene expression in PBMC of these patients showed that there was strong up-regulation of IFN-␥ transcripts upon stimulation with leishmania antigen, in contrast to the baseline levels of IL-10 mRNA. IL-10 suppressed IFN-␥ production by 48% in cell cultures from cutaneous leishmaniasis patients and by 86% in cell cultures from healthy subjects stimulated with purified protein derivative, whereas in similar conditions IL-10 suppressed IFN-␥ production by 19% in cell cultures from mucosal leishmaniasis patients stimulated with leishmania antigen. TGF-␤ suppressed IFN-␥ levels to a greater extent in healthy subjects than in mucosal leishmaniasis and cutaneous leishmaniasis patients. These data indicate that a poorly modulated T-cell response in mucosal leishmaniasis patients leads to production of high levels of proinflammatory cytokines, such as IFN-␥ and TNF-␣, as well as a decreased ability of IL-10 and TGF-␤ to modulate this response. These abnormalities may be the basis for the pathological findings observed in this disease.

Human infection with Leishmania braziliensis can lead to cutaneous leishmaniasis (CL) or mucosal leishmaniasis (ML). We hypothesize that the intense tissue destruction observed in ML is a consequence of an uncontrolled exacerbated inflammatory immune response, with cytotoxic activity. For the first time, this work identifies the cellular sources of inflammatory and antiinflammatory cytokines, the expression of effector molecules, and the expression of interleukin-10 (IL-10) receptor in ML and CL lesions by using confocal microscopy. ML lesions displayed a higher number of gamma interferon (IFN-␥)-producing cells than did CL lesions. In both ML and CL, CD4؉ cells represented the majority of IFN-␥-producing cells, followed by CD8 ؉ cells and CD4 ؊ CD8 ؊ cells. The numbers of tumor necrosis factor alpha-positive cells, as well as those of IL-10-producing cells, were similar in ML and CL lesions. The effector molecule granzyme A showed greater expression in ML than in CL lesions, while inducible nitric oxide synthase did not. Finally, the expression of IL-10 receptor was lower in ML than in CL lesions. Thus, our data identified distinct cytokine and cell population profiles for CL versus ML patients and provide a possible mechanism for the development of ML disease through the demonstration that low expression of IL-10 receptor is present in conjunction with a cytotoxic and inflammatory profile in ML.

The clinical spectrum of leishmaniasis and control of the infection are influenced by the parasite-host relationship. The role of cellular immune responses of the Th1 type in the protection against disease in experimental and human leishmaniasis is well established. In humans, production of IFN-γ is associated with the control of infection in children infected by Leishmania chagasi. In visceral leishmaniasis, an impairment in IFN-γ production and high IL-4 and IL-10 levels (Th2 cytokines) are observed in antigen-stimulated peripheral blood mononuclear cells (PBMC). Moreover, IL-12 restores IFN-γ production and enhances the cytotoxic response. IL-10 is the cytokine involved in down-regulation of IFN-γ production, since anti-IL-10 monoclonal antibody (mAb) restores in vitro IFN-γ production and lymphoproliferative responses, and IL-10 abrogates the effect of IL-12. In cutaneous and mucosal leishmaniasis, high levels of IFN-γ are found in L. amazonensis-stimulated PBMC. However, low or absent IFN-γ levels were observed in antigen-stimulated PBMC from 50% of subjects with less than 60 days of disease (24 ± 26 pg/ml). This response was restored by IL-12 (308 ± 342 pg/ml) and anti-IL-10 mAb (380 ± 245 pg/ml) (P<0.05). Later during the disease, high levels of IFN-γ and TNF-α are produced both in cutaneous and mucosal leishmaniasis. After treatment there is a decrease in TNF-α levels (366 ± 224 pg/ml before treatment vs 142 ± 107 pg/ml after treatment, P = 0.02). Although production of IFN-γ and TNF-α might be involved in the control of parasite multiplication in the early phases of Leishmania infection, these cytokines might also be involved in the tissue damage seen in tegumentary leishmaniasis.Correspondence