MUC17 is an essential small intestinal glycocalyx component that is disrupted in Crohn's disease.

Crohn's disease (CD) is the chronic inflammation of the ileum and colon triggered by bacteria, but insights into molecular perturbations at the bacteria-epithelium interface are limited. We report that membrane mucin MUC17 protects small intestinal enterocytes against commensal and pathogenic bacteria. In non-inflamed CD ileum, reduced MUC17 levels correlated with a compromised glycocalyx, allowing bacterial contact with enterocytes. Membrane mucin MUC17 protects enterocytes against bacterial attachment and constitutes an early defect in Crohn's disease.