OCLN and colitis: From the clinicopathologic features of colitis, impaired intestinal mucosal barrier function and microflora have been shown to be often associated with colitis, accompanied by reduced expression levels of secretory immunoglobulin A (sIgA) and tight junction proteins (ZO-1 and Occludin; Yang et al., 2015; Li et al., 2018; Wang et al., 2019; Fu et al., 2021).