CD47 and neoplasm: In contrast, significant PMN-mediated cytotoxicity against ATRA pretreated HSB-2 cells was only achieved with the IgA2 isotype of daratumumab (up to 45.1 ± 7.9% specific tumor cell lysis vs 6.2 ± 1.9% lysis with CD47 blockade alone) and was increased to 68.0 ± 6.4% after combining ATRA treatment and CD47 blockade.