FcγRI plays a critical role in patients with ulcerative colitis relapse

Ulcerative colitis (UC) is a disease that frequently relapses and affects more than 0.1% general population; the underlying mechanism is poorly understood. Published data show that polymorphonuclear neutrophils (PMN) contribute to the pathogenesis of UC. This study aims to identify antigen (Ag)‐specific PMNs and investigate their role in UC relapse. In this study, the correlation between PMN activities and UC relapse was assessed in a group of UC patients. A UC mouse model was developed to expand the findings of UC patient study. The results showed that a positive correlation was detected between the high PMN activities and the food Ag‐specific IgG amounts in colon biopsies of UC patients. UC patient‐derived Ag‐specific PMNs could be activated upon exposure to food specific Ag. The Ag/FcγRI complexes were detected on the surface of PMNs in UC patients. Re‐exposure of sensitized PMNs to specific Ag triggered PMN activation and induced UC‐like inflammation in the mouse colon. We conclude that FcγRI plays a critical role in UC relapse. Inhibition of FcγRI can efficiently inhibits experimental UC. Specific antigens bind the FcγRI on the surface of antigen‐specific PMNs to induce PMNs to release proinflammatory cytokines, and thus, trigger the colon inflammation relapse.