Human platelet antigens – 2013

Abstract

To date, 33 human platelet alloantigens (HPAs) have been identified on six functionally important platelet glycoprotein (GP) complexes and have been implicated in alloimmune platelet disorders including foetal and neonatal alloimmune thrombocytopenia (FNAIT), posttransfusion purpura (PTP) and multitransfusion platelet refractoriness (MPR). The greatest number of recognized HPA (20 of 33) resides on the GPIIb/IIIa complex, which serves as the receptor for ligands important in mediating haemostasis and inflammation. These include HPA-1a, the most commonly implicated HPA in FNAIT and PTP in Caucasian populations. Other platelet GP complexes, GPIb/V/IX, GPIa/IIa and CD109, express the remaining 13 HPAs. Of the recognized HPAs, 12 occur as six serologically and genetically defined biallelic 'systems' where the -a form designates the higher frequency allele and the -b form, the lower. Twenty-one other HPAs are low-frequency or rare antigens for which postulated higher frequency -a alleles have not yet been identified as antibody specificities. In addition to the HPA markers, platelets also express ABO and human leucocyte antigen (HLA) antigens; antibodies directed at the former are occasionally important in FNAIT, and to the latter, in MPR.

Characterization of a Human Platelet Antigen-1a–Specific Monoclonal Antibody Derived from a B Cell from a Woman Alloimmunized in Pregnancy

“…MAIPA inhibition assay mAb 26.4 F(ab9) 2 fragment was prepared using Pierce F(ab9) 2 Preparation Kit (Pierce, Appleton, WI). The purified F(ab9) 2 fragment concentration (0.7 mg/ml) was determined by spectrophotometry from the absorbance at 280 nm using an extinction coefficient of 1.4 L 3 g 21 3 cm 21 .…”

“…In populations of European descent, the HPA-1a and HPA-1b allele frequencies are ∼0.85 and 0.15, respectively, and ∼2% of this population is HPA-1b-homozygous. In other ethnic groups, the HPA-1b allele is less common (2). Integrin b3 forms part of the fibrinogen receptor (aIIbb3), which is the most abundant integrin on platelets.…”

Maternal anti-platelet β3 integrins impair angiogenesis and cause intracranial hemorrhage

“…FNAIT occurs in approximately 0.5 to 1.5 per 1,000 live-born neonates, but this does not include miscarriages in utero, as has been reported (4,5). There are 33 reported human platelet antigens (HPAs) that can be recognized by maternal antibodies in FNAIT, and approximately half are located in the different regions of the extracellular domain of GPIIIa (β3 integrin [β3] subunit) (1,6). At least one antigen (HPA-2) is located on GPIbα (6,7).…”

“…There are 33 reported human platelet antigens (HPAs) that can be recognized by maternal antibodies in FNAIT, and approximately half are located in the different regions of the extracellular domain of GPIIIa (β3 integrin [β3] subunit) (1,6). At least one antigen (HPA-2) is located on GPIbα (6,7). In people of mixed European descent, 80% to 90% of cases are due to antibodies targeting HPA-1a on β3.…”

Genotipagem de grupos sanguíneos por meio de microarranjos líquidos

“…Entretanto, esse perfil genotípico dos doadores predispõe à aloimunização de doentes falciformes, com perfil fenotípico negroide, reiterando a necessidade de transfusões com fenótipo compatível como profilaxia à aloimunização. 6,7 .…”