The M290 monoclonal antibody reacts with mouse CD103 also known as integrin αE (ITGAE). CD103 is an integrin protein that binds integrin beta 7 to form the complete heterodimeric integrin molecule αEβ7. CD103 is expressed widely on intraepithelial lymphocyte (IEL) T cells (both αβ T cells and γδ T cells) and on some peripheral regulatory T cells. It has also been reported on lamina propria T cells. A subset of dendritic cells in the gut mucosa and in mesenteric lymph nodes also expresses CD103. The main ligand for CD103 is E-cadherin, an adhesion molecule expressed by epithelial cells. CD103 is thought to facilitate the interactions of T cells with epithelial cells during T cell maturation and effector functions. The M290 antibody is reported to neutralize CD103 in vivo.