Different regulation of H and A antigen on platelets and RBCs. (A) H antigen expression (FITC-UEA1) on group O, A1, and A2 donors by flow cytometry. (B-C) The distribution of H (B, % UEA1+) and A antigens (C, % HPA+) on platelets in a population of group O, A1, and A2 donors. (D-E) The distribution of H (D, % UEA1+) and A (E, % HPA+) antigens on RBCs in a population of group O, A1, and A2 donors. Note the absence of H and A on A2 platelets, whereas H is increased on A2 RBCs. The relative expression of H and A also differs between A1 RBCs and platelets as well. Horizontal brackets (B-E) indicate UEA1+ fluorescence. Cells left of the bracketed area were considered UEA1-negative. (F-G) Blood group H (% UEA1+) and A (% HPA+) expression in individual group A platelet donors. (F) On platelets, A and H are proportionately coexpressed, where y = 0.15 + 0.93x. (G) Blood groups H and A are inversely expressed on RBCs (y = 103.3-0.53x), with 2 distinct clusters representing A1 and A2 donors.
