Blood group antigens on plasma vWF after ABO minor mismatched BMT. (A) The recipient (patient M.N.; type AB) who suffered from acute lymphocytic leukemia was transplanted with bone marrow from an HLA-matched but ABO minor mismatched donor (sister; type O). Plasma and red blood cells (RBC) were serially collected from the recipient. The reactivity of RBC against anti-A and -B antibodies was expressed as positive (+), negative (−) or mixed field (±) observations. The anti-blood group antibody production was expressed as titers. Each plasma sample was diluted to 1:20 with TwTBS and vWF in plasma was measured by ELISA using anti-vWF antibody and the concentration of vWF (□), the binding of anti-A (•), anti-B MoAbs (○) and UEA-I (▴) were monitored. Data express the average of three measurements. Arrow indicates reactivities of the donor. (B) HLA-matched and ABO minor mismatched BMT between patient K.Y. with type A who suffered from severe aplastic anemia at the second remission and the donor with type O (father). Concentration of vWF (□) and the blood group A antigen (•) on vWF in 1:80 diluted plasma were monitored. RBC showed the mixed field to anti-A from 14 days after transplantation.