Expression of A or B antigen on human red cells of ABO variants including A2, A3, A2B3 and B2 were analyzed using flow cytometry (FCM). Profiles of the variants were different from those of A1 or B red cells; proportions of anti-A positive cells in A2 and A3 red cells were 49.5% and 7.2%, respectively whereas that in A1 was 81.4%. These results seemed to be associated with A antigen amounts of the corresponding red cells. Therefore, a quantitative analysis of A or B antigen on red cells with FCM would be helpful in characterization of variant red cells.
