Relationship between α₂ 807 genotype and platelet α₂β₁ levels. The level of platelet α₂β₁ was determined by flow cytometry using the binding of monoclonal antibody 12F1. The corrected and normalized MFI values are indicated on the ordinate, and the results from each donor are plotted as a function of donor genotype with respect to the 807C and 807T alleles. Values are single measurements from each of 30 individuals but are representative of repeated measurements performed on several occasions. The boxed area in each data set represents the mean ± 1 SD. The difference in the means between donor groups is statistically significant (CC v CT, P < .05; and CC v TT, P < .05).