Leprosy is not only a bacteriological disease but also an immunological disease, in which T helper17 and CD4+ CD25highFoxP3+ regulatory T cells (T-regs), among others, may play a role. We aimed to evaluate serum levels of interleukin (IL)-17, IL-22 (Th17 cytokines), IL-10 and transforming growth factor (TGF)-β (down regulatory cytokines) in 43 untreated leprosy patients and 40 controls by enzyme-linked immunosorbent assay, and to assess circulating CD4+ CD25highFoxP3+T-regs in patients using flow cytometry. Patients were grouped into tuberculoid, pure neural, borderline, lepromatous, type 1 reactional leprosy, and erythema nodosum leprosum. IL-10 and TGF-β were significantly higher in patients as compared to controls (p < 0.001), while IL-17, but not IL-22, was significantly lower (p < 0.001), with no significant difference comparing patients’ subgroups. Significantly higher CD4+ CD25highFoxP3+T-regs levels was detected in tuberculoid, type 1 reaction and pure neural leprosy, while the lowest levels in erythema nodosum leprosum (p < 0.001). TregsFoxP3 expression% was significantly lower in pure neural leprosy than other patients’ subgroups (p < 0.05). T-regs/T-effs was lowest in erythema nodosum leprosum (p < 0.05). TGF-β correlated negatively with TregsFoxP3 expression% and T-effs% (p = 0.009 and 0.018 respectively). Leprosy is associated with defective IL-17 and overproduction of IL-10 and TGF-β. Tuberculoid, type 1 reaction and pure neural leprosy express significantly higher circulating T-regs, consistent with effector immune mechanisms activation, but with lower TregsFoxP3 expression (in pure neural leprosy). Erythema nodosum leprosum is characterized by deficient T-regs and increased TregsFoxP3 expression%. The present study pinpointed a potential role of Th17, CD4+ CD25highFoxP3+T-regs, and probably CD4+ CD25+IL-10+ T regulatory cells 1 (Tr1), and Th3 in leprosy.
