In turn, genetic inactivation of S100a9 protected against experimental enteritis and colitis, and pharmacologic inhibition of S100A9 ameliorated chronic colitis.<h4>Conclusions</h4>Collectively, this study links the detection of fecal S100A9 dimers with clinical and endoscopic disease activity in IBD and identifies inflammatory actions of S100A8 and S100A9 homodimers in the intestine. Here, S100A9 is linked to enteritis.