PTPRC and leukemia: Similar to the primary AML models, IgG2σ C47B222-(CHO) significantly cleared splenic leukemia burden in NSG mice engrafted with HL60 cells and demonstrated a significant albeit small decrease in bone marrow leukemia burden (98.6 vs 75.6% CD45+ cells PBS vs IgG2 C47B222-(CHO); Figure 4b).