There are some published cases of severe leptospirosis in which corticosteroid administration improved survival among patients, while there is still insufficient evidence to suggest the effectiveness of immunosuppressive treatments in severe leptospirosis.57, 58, 59 In this study, we observed an alleviation of pulmonary hemorrhage in TLR4−/− mice, possibly due to suppression of the ‘storm’ of proinflammatory cytokine production. Here, TLR4 is linked to leptospirosis.