National Blood Transfusion Service

Molecular biology for platelet alloantigen typing

Hitherto, full investigation of patients with alloimmunization to platelet-specific antigens has been difficult due to the limited availability of both typing reagents and panels of typed platelets. Following recent advances in the understanding of the molecular and genetic basis of platelet alloantigens, it is now possible to genotype individuals for the alleles coding for the epitopes of four platelet antigen systems (HPA-1-4). This is based on the finding that the two alleles differ by only a single base pair substitution, resulting in one amino acid difference in the relevant platelet glycoprotein. The technique involves amplification of the relevant segments of genomic DNA from any nucleated cell by the polymerase chain reaction, followed by restriction fragment length polymorphism analysis. The technique allows investigation of thrombocytopenic individuals and fetuses/neonates, and can be readily applied to large-scale typing of platelet donors.