Probable genetic linkage between genes coding for platelet-specific antigens of the PlA and Bak systems.

Studies of the inheritance of the platelet-specific alloantigens PlA1/PlA2 and Baka/Bakb in informative families provided evidence that the genes determining PlA and Bak antigens are in close genetic linkage (P = .004). In 154 normal, unrelated Caucasian subjects it was found that the antigen PlA1 is associated with Baka and the antigen PlA2 with Bakb more often than would be expected by chance (P less than .05). Bak and PlA antigens are carried on platelet membrane glycoproteins IIb and IIIa, respectively, which are decreased or absent in the inherited platelet disorder Glanzmann's thrombasthenia. Thus, the findings suggest that the defect in this disease involves two closely linked genes.