Only recently, knockout mouse models were applied in studies on the pathogenesis of leptospirosis. Current data suggest an important role of innate immunity receptors and interferon gamma dependant cellular response on protection. It is not clear, however, whether T helper cell polarization influences on outcome of leptospiral infection. We report findings of experimental infection of C57BL/6 (interferon gamma or tumor necrosis factor alpha receptor deficient) and BALB/c (interleukin 4 deficient) mice infected by pathogenic Leptospira interrogans serovar Copenhageni. Specific cytokine gene deficiency had no impact on outcome since all animals survived. TNFR knockout mice, however, exhibited more severe residual renal inflammation during convalescence thus suggesting this cytokine is important in early control of infection, protecting kidneys from relevant pathology.