Complement-dependent hematopoietic inhibitors in the sera of patients with aplastic anemia and paroxysmal nocturnal hemoglobinuria.

The sera of 14 out of 48 patients with aplastic anemia and four out of nine patients with paroxysmal nocturnal hemoglobinuria (PNH) contained complement-dependent hematopoietic inhibitory activity against allogeneic marrow progenitor cells. Some sera with hematopoietic inhibitory activity, however, demonstrated no effect on autologous marrow progenitor cells. Hematopoietic inhibitory activity was absorbed by pooled, packed platelets. Serum hematopoietic inhibitory activity was present in both IgM and IgG fractions. These data suggested that serum hematopoietic inhibitors are alloantibodies and might be associated with graft rejection in the transplanted marrow of patients with aplastic anemia and PNH.