CD6 and cancer: The more modest effect of anti-CD318 could be attributable to a dual effect of UMCD6: rapid internalization of CD6 prevents or reverses engagement of CD6 by its ligands on cancer cells, and UMCD6 also directly activates the cytotoxic properties of CD8+ and NK cells, whereas anti-CD318 does not have any effect on lymphocyte cytotoxicity (36, 52).