CD103, an integrin mediating lymphocyte retention in epithelial tissues. CD103+ Treg suppressed T effector cell activation more strongly than CD103(neg) Treg. Expression of CD103 on Treg closely correlated with intratumoral levels of transforming growth factor β (TGF-β) and could be induced in a TGF-β-dependent manner by tumor cell lines [PMID: 21207371].