Decline in the percentage of GPI-anchored protein–negative granulocytes after transplantation. The percentage of GPI-anchored protein–negative granulocytes was measured by flow cytometry (CD15⁺/CD66b^–/CD16^–) in 5 patients before and multiple time points after nonmyeloablative hematopoietic cell transplantation. Detection of GPI-negative granulocytes after neutrophil recovery is consistent with the conditioning regimen being nonmyeloablative. The initial decline in GPI-negative populations occurred as a consequence of nonmyeloablative conditioning. The complete erradication of GPI-negative neutrophils in all patients by 25 to 118 days (median, 85 days) after transplantation occurred as a consequence of a graft-versus-host hematopoietic effect.