CD8A and cancer: Anti-CD318 produces a more modest effect on cancer cell death and survival compared to UMCD6, which is attributable to a dual effect of UMCD6: 1) rapid internalization of CD6 prevents or reverses engagement of CD6 by its ligand CD318 on cancer cells; and 2) UMCD6 directly activates the cytotoxic properties of CD8+, NK-T and NK cells.