CD47 and acute myeloid leukemia: Since the anti-leukemic activity of IgG1 C47B222-(CHO) anti-CD47 mAb does not seem to correlate with CD47 receptor density across the different AML models (data not shown), the differential activity of IgG1 C47B222-(CHO) may potentially be ascribed to bone marrow engraftment at the time of treatment start.