REG4 is a secreted contains one C-type lectin domain, high expressed in the gastrointestinal tract, including jejunum, ileum, appendix, pancreas and small intestine. REG4 can be up-regulated by mucosal injury from active Crohn’s disease or ulcerative colitis. In the acid environment, REG4 can maintain carbohydrate recognition activity. REG4 may be involved in inflammatory and metaplastic response of the gastrointestinal epithelium.