The role of IL-4 has been studied in mice, but the resistance of BALB/c/IL-4ko mice to the infection with L. interrogans serovar Copenhageni strain Fiocruz L1-130 was comparable to WT BALB/c, suggesting that IL4 does not play a major role in leptospirosis in these mice (46). Here, IL4 is linked to infection.