Immune-Mediated Hematopoietic Failure after Allogeneic Hematopoietic Stem Cell Transplantation: A Common Cause of Late Graft Failure in Patients with Complete Donor Chimerism

Late graft failure (LGF) without evidence of residual recipient cells is a serious complication after allogeneic hematopoietic stem cell transplantation (allo-SCT) and often requires stem cell infusion from the same donor when the patient fails to respond to conventional therapies. We screened the peripheral blood (PB) of 14 patients who developed donor-type LGF at 2 to 132 months after allo-SCT for the presence of the markers for immune-mediated bone marrow (BM) failure. Increased glycosylphosphatidyl inositol-anchored protein-deficient (GPI-AP^-) leukocytes, which accounted for .009% to 0.147% of the total granulocytes, were detected in 5 patients (severe aplastic anemia, n = 2; follicular lymphoma, n = 1; acute lymphoblastic leukemia, n = 1; myelodysplastic syndromes; n = 1) and 4.7% to 81.2% HLA-allele-lacking leukocytes (HLA-LLs) were detected in 2 patients (acute myelogenous leukemia, n = 1; and myelodysplastic syndromes, n = 1). Three of the 5 patients with increased GPI-AP^- leukocytes were treated with antithymocyte globulin (ATG), and 2 patients achieved transfusion independence. These results suggest that immune mechanisms that are similar to acquired aplastic anemia underlie condition of approximately one-half of the patients with donor-type LGF, and that in patients with increased GPI-AP^- cells, donor-derived hematopoiesis may be restored by ATG therapy alone without donor stem cell infusion.