Cell adhesion protein that mediates homophilic cell adhesion in a calcium-independent manner. Plays a role as coinhibitory receptor in immune response, insulin action and functions also as an activator during angiogenesis. Cell adhesion protein that mediates homophilic cell adhesion in a calcium-independent manner. Promotes populations of T cells regulating IgA production and secretion associated with control of the commensal microbiota and resistance to enteropathogens.