PLTs of blood group A1 donors express increased surface A antigen owing to apheresis and prolonged storage

In contrast to RBC transfusion, where ABO mismatch is potentially lethal, immunologic ABO matching has been considered less critical for PLTs. Nonetheless, PLTs bear ABO blood group antigens, some of them expressing very high levels.

The expression of A antigen was investigated by flow cytometry on resting and stimulated human PLTs of 100 A and 10 O group donors, as well as on 17 PLT concentrates (PCs) after apheresis and daily during a 6-day storage, to determine possible changes in expression of A antigen on PLT surface.

Considerable variation of A antigen expression on PLT surface of A1 group individuals was observed; A2 group PLTs could not be distinguished from O group PLTs. The variability of A antigen on A group PLTs also became evident on investigating PLT lysates by ELISA. A1 group PCs showed a significant increase of A antigen expression on their surface owing to apheresis (p = 0.001) and to storage (p = 0.0091).

Apheresis and prolonged storage of A1 group PCs independently led to overexpression of A antigen on the PLT surface. This may make such PCs more susceptible to destruction by anti-A of O or B group recipients.