Human platelet antigen (HPA)

Human platelet antigens (HPAs), commonly called platelet-specific antigens, are polymorphic structures present on the surface of platelet membrane glycoproteins, most notably integrin complexes (e.g., GPIIb/IIIa, GPIa/IIa, GPIb/IX, and CD109)[1][3][4][5]. These polymorphisms arise mainly from single nucleotide polymorphisms (SNPs) leading to single amino acid substitutions, creating immunologically distinct alleles[3][4]. Exposure to incompatible HPAs via transfusion, pregnancy, or transplantation can trigger the development of alloantibodies, causing immune destruction of platelets and leading to serious clinical syndromes such as neonatal alloimmune thrombocytopenia, post-transfusion purpura, and platelet transfusion refractoriness[1][2][3][4]. The International Society of Blood Transfusion (ISBT) has established standardized numeric nomenclature for HPAs, most commonly referenced as HPA-1a, HPA-1b, and so forth[3]. HPAs themselves are not receptors, enzymes, or classical therapeutic targets but rather genetic determinants of immune compatibility, significant especially in transfusion medicine and perinatal care. Detection and matching of HPA types rely on both serological assays (e.g., MAIPA) and molecular-genotyping approaches[1][3][4]. **Notes on correctness:** "Platelet-specific antigens" is a functional/generic group term, not a single discrete molecule or classical drug target like a receptor or enzyme. It refers to a family of surface antigens (the HPAs) rather than an individual targetable molecule, so it is too broad and non-specific for most drug-targeting frameworks[3][4][5]. Each specific HPA (e.g., HPA-1a) can be individually described if needed, but "Platelet-specific antigens" does not refer to a unique molecular entity.

Other names

Platelet-specific antigenPlatelet alloantigen

Immune modulation by IVIG (suppresses antibody response); Immunosuppression by corticosteroids.