Study on the expression of ABH antigens on platelets

We recently examined a case of refractoriness to HLA-matched, ABO-incompatible platelet transfusions. The transfused platelets that were rapidly cleared from the circulation of the recipient expressed an amount of B antigen more than 20 times that expressed by the blood group B platelets that were successfully transfused to the recipient. These observations led us to conduct enzyme-linked immunosorbent assay (ELISA) and immunoblotting studies of the amount of blood A and B antigens expressed on the surface of platelets from randomly selected donors. The donors were clearly classified, according to the amount of A or B antigen expressed on their platelets, into two phenotypes, the high-expression and low-expression phenotypes. By ELISA, 7% of the examined donors were determined as belonging to the high-expression phenotype of either A or B antigen. The high-expression phenotype was independent of secretor phenotype. In transferase activity assay, a donor with high expression of B had increased B transferase activity in her serum, which suggested that the high-expression phenotype might be under the control of the glycosyltransferase gene. Family studies showed a dominant inheritance pattern of the high-expression phenotype. This report provides evidence that the expression of ABH antigens on platelets is genetically determined and that the ABO group should be given some attention in platelet transfusions.