Hydrogen peroxide release by bacteria suppresses inflammasome-dependent innate immunity

Hydrogen peroxide (H(2)O(2)) has a major function in host-microbial interactions. Although most studies have focused on the endogenous H(2)O(2) produced by immune cells to kill microbes, bacteria can also produce H(2)O(2). How microbial H(2)O(2) influences the dynamics of host-microbial interactions is unclear. Here we show that H(2)O(2) released by Streptococcus pneumoniae inhibits inflammasomes, key components of the innate immune system, contributing to the pathogen colonization of the host. We also show that the oral commensal H(2)O(2)-producing bacteria Streptococcus oralis can block inflammasome activation. This study uncovers an unexpected role of H(2)O(2) in immune suppression and demonstrates how, through this mechanism, bacteria might restrain the immune system to co-exist with the host.