Platelet alloantigens and transfusion.

Platelet transfusion therapy became to be largely used in the last 20 years. This development was related to the progress of plastic bags and of blood cell separators. In parallel the platelet immunology has moved from serological techniques to molecular biology. The biochemical characterization of platelet antigen and the genetic basis of the polymorphism was discovered in the last years. The platelet RNA PCR amplification and specific oligonucleotide typing are now accessible to several laboratories. Five major human platelet antigen (HPA) systems are completely characterized. HPA-1 (PLA, Zw) localized on platelet glycoprotein GPIIIa correspond to a single amino acid substitution (leu<==> Pro 33). HPA-2 (Ko, Sib) present on GPIb is due to a Thre<==>Met substitution in 145. HPA-3 formerly Bak, Lek correspond to a polymorphism in 843 (Ile<==>ser) on GPIIb. HPA-4 (Pen, Yuk) as HPA1 is on GPIIIa but in a different location (Arg<==>Gln 143). HPA-5 (Br, He, Zav) and HPA-6 (Ca, Tu) are on GPIa and GPIIIa respectively. The major progress made in the field of platelet immunology has not yet been largely applied to the clinical situation of platelet transfusion. We can hope that it could help in the future to a better platelet-transfusion compatibility and consequently an improved clinical efficacy of platelet transfusion.