Most cases of nonengrafting AML do not engraft in the B2m^-/- NOD/SCID model. Ten million mononuclear cells from 23 different AML patients were injected into both NOD/SCID () and B2m^-/- NOD/SCID (▪) mice in paired experiments. Six weeks later, bone marrow engraftment was assessed via flow cytometry. AML engraftment was recorded if human CD33⁺/CD45⁺ myeloid cells were present without an accompanying CD19⁺/CD45⁺ B-cell population. Ten of 12 AML cases that failed to engraft in the NOD/SCID assay did not engraft in the B2m^-/- NOD/SCID model.