Elimination of alloantibodies by immunoablative high dose cyclophosphamide

Background Alloimmunization is a major problem for patients being considere d for solid organ transplantation and in patients who require blood transfu sion support. We previously demonstrated that high-dose cyclophosphamide (2 00 mg/kg) without hematopoietic stem cell transplantation leads to durable complete remissions in aplastic anemia and other autoimmune disorders. We n ow examine the ability of high-dose cyclophosphamide to eliminate alloreact ivity. Methods. IgG-specific antibodies to HLA class I were assayed using enzyme-l inked immunosorbent assays in 18 consecutive patients with severe aplastic anemia before and after treatment with high-dose cyclophosphamide. Results. Anti-HLA antibodies were detected before or shortly after therapy in 5 of the 18 patients studied. Complete remission of aplastic anemia was achieved in four of these five patients. High-dose cyclophosphamide markedl y reduced anti-HLA antibody titers in these four patients; they were comple tely eradicated in three patients. Only one patient did not achieve signifi cant reduction in the alloantibody titer after high-dose cyclophosphamide. Conclusions. High-dose cyclophosphamide without stem cell transplantation c an eradicate HLA-specific alloantibody.