F11R, also known as CD321, belongs to the immunoglobulin superfamily. It seems to plays a role in epithelial tight junction formation. Tight junctions represent one mode of cell-to-cell adhesion in epithelial or endothelial cell sheets, forming continuous seals around cells and serving as a physical barrier to prevent solutes and water from passing freely through the paracellular space. F11R protein can act as a receptor for reovirus, a ligand for the integrin LFA1, involved in leukocyte transmigration, and a platelet receptor.