Regenerating islet-derived protein 4 (REG4) is also known as Gastrointestinal secretory protein (GISP), REG-like protein (RELP). REG4 contains one C-type lectin domain. REG4 has calcium-independent lectin displaying mannose-binding specificity and able to maintain carbohydrate recognition activity in an acidic environment. REG4 may be involved in inflammatory and metaplastic responses of the gastrointestinal epithelium.