Determinants of ABH expression on human blood platelets

Platelets express ABH antigens, which can adversely effect platelet transfusion recovery and survival in ABH-incompatible recipients. To date, there has been no large, comprehensive study comparing specific donor factors with ABH expression on platelet membranes and glycoconjugates. We studied ABH expression in 166 group A apheresis platelet donors by flow cytometry, Western blotting, and thin layer chromatography relative to donor age, sex, A ₁/A₂ subgroup, and Lewis phenotype. Overall, A antigen on platelet membranes, glycoproteins, and glycosphingolipids was linked to an A₁ red blood cell (RBC) phenotype. Among A₁ donors, platelet ABH varied significantly between donors (0%-87%). Intradonor variability, however, was minimal, suggesting that platelet ABH expression is a stable, donor-specific characteristic, with 5% of A₁ donors typing as either ABH high- or low-expressers. Group A₂ donors, in contrast, possessed a Bombay-like phenotype, lacking both A and H antigens. Unlike RBCs, ABH expression on platelets may be determined primarily by H-glycosyltransferase (FUT1) activity. Identification of A₂ and A₁ low expressers may increase the availability and selection of crossmatched and HLA-matched platelets. Platelets from group A₂ may also be a superior product for patients undergoing A/O major mismatch allogeneic progenitor cell transplantation.