Cell adhesion molecule that mediates both heterotypic cell-cell contacts via its interaction with CD6, as well as homotypic cell-cell contacts . Promotes T-cell activation and proliferation via its interactions with CD6 . Contributes to the formation and maturation of the immunological synapse via its interactions with CD6 . Mediates homotypic interactions with cells that express ALCAM . Required for normal hematopoietic stem cell engraftment in the bone marrow . Mediates attachment of dendritic cells onto endothelial cells via homotypic interaction . Inhibits endothelial cell migration and promotes endothelial tube formation via homotypic interactions . Required for normal organization of the lymph vessel network. Required for normal hematopoietic stem cell engraftment in the bone marrow. Plays a role in hematopoiesis; required for normal numbers of hematopoietic stem cells in bone marrow. Promotes in vitro osteoblast proliferation and differentiation (By similarity). Promotes neurite extension, axon growth and axon guidance; axons grow preferentially on surfaces that contain ALCAM. Mediates outgrowth and pathfinding for retinal ganglion cell axons (By similarity).