CD96 and plasma cell myeloma: Importantly, attempts to demonstrate a direct role of CD96 as activator for NK cell-mediated cytotoxicity in vitro failed because neutralizing anti-CD96 mAb did not reveal any effect of hCD96 in killing of ovarian carcinoma cells (57) or myeloma cell lines (58) and of mCD96 in elimination of RMA, RMA-S, or YAC-1 tumor cells (6).