During the process of inflammatory bowel disease, intestinal mucosal integrity and barrier function are impaired, which leads to translocation of bacterial antigens, thus inducing expression of pro-inflammatory cytokines and down-regulation of tight junction (TJ) proteins, such as ZO-1, occludin and claudin-1 protein, and occludin redistribution56, 57. This evidence concerns the gene CLDN1 and inflammatory bowel disease.