Transformation of blood groups B (III) and A (II) into AB (IV) after bone marrow transplantation from HLA identical sibs with groups A (II) and B (III)

After HLA-identical transplantation of bone marrow to two patients with leukemia with erythrocytic phenotype B (III) Rh+ and A (II) Rh+ from two donor sibs with opposite blood groups A (II) Rh- and B (III) Rh+, 10–15% erythrocytes of phenotype AB were produced for several months in both recipients, which may be due to the formation of hybrid hemopoietic cells.