CD103 (Integrin αE) is an integrin subunit that is expressed on intraepithelial lymphocytes, epithelial dendritic cells, lamina propria-derived dendritic cells, a subpopulation of lamina propria T cells, a small subset of peripheral lymphocytes, namely T reg cells, and on activated and TGF-β stimulated lymphocytes. CD103 is in mature form cleaved into two disulfide-linked chains (C-terminal 150 kDa chain and N-terminal 25 kDa chain). It heterodimerizes with integrin β7 subunit to form αE/β7 integrin (mucosal lymphocyte 1 antigen), which through binding E-cadherin mediates homing of lymphocytes to the intestinal epithelium, and, in addition to the role in adhesion, may serve as an accessory molecule for intraepithelial lymphocyte activation.