A1 and B antigen expression on platelets from 100 normal-expresser group A1 and group B blood donors determined by flow cytometry.
Values shown on the ordinate are the ratios of the mean fluorescent signal obtained with serum containing anti-A,B to that obtained with ABO-compatible serum used at the same dilution. The horizontal line indicates the mean for the total population plus 2 SD. Platelets with A1 (A) or B antigen (B) levels that exceeded the mean plus 2 SD (indicated by triangles) were tested a second time, and the results were averaged (horizontal bars). We retested 6 A1and 5 B platelet preparations with lower antigen values, and their averages are indicated by the horizontal bars. The platelets from 7 A1 and 4 B donors (indicated by triangles) expressed levels of the A1 or B antigen, which were consistently at least 2 SD above the mean for the total population.
