title: A V740L mutation in glycoprotein IIb defines a novel epitope (War) associated with fetomaternal alloimmune thrombocytopenia.
abstract: BACKGROUND
  Most recently described human platelet antigens (HPAs) have been detected in cases of fetomaternal alloimmune thrombocytopenia (FMAIT) where the mother has been immunized against a low-frequency antigen that the fetus has inherited from the father. Low-frequency antigens are not represented in normal panel platelets (PLTs) and antibody detection and identification in such cases requires incubation of maternal serum with paternal PLTs and definition of the causative mutation.
  
  
  METHODS
  A suspected case of FMAIT was investigated for PLT-specific antibodies using a panel of both HPA-typed and paternal PLTs. HPA typing was performed by polymerase chain reaction with sequence-specific primers and further DNA analysis was performed using direct sequencing of the coding regions of the ITGA2B and ITGB3 genes.
  
  
  RESULTS
  Maternal antibodies reactive only with paternal PLTs were localized to glycoprotein (GP)IIb/IIIa using the monoclonal antibody immobilization of PLT antibody assay. A single-nucleotide polymorphism was detected in Exon 23 of ITGA2B in the father and affected child, which predicted a V740L substitution in the mature protein. Recombinant V740L mutated GPIIb expressed in HEK293 cells was specifically recognized by maternal antibodies. The polymorphism was not detected either in the mother or in a cohort of 100 donors.
  
  
  CONCLUSIONS
  The V740L polymorphism defines a new low-frequency antigen implicated in two cases of FMAIT in a single family. Low-frequency HPAs are clinically important and their elucidation requires both crossmatch studies and gene sequencing in cases where there is strong clinical evidence of FMAIT but initial laboratory investigations do not support the diagnosis.
authors.affiliation: Histocompatibility and Immunogenetics, NHSBT, Bristol, United Kingdom; Bristol Institute for Transfusion Sciences, Bristol, United Kingdom; Irish Blood Transfusion Service, Dublin, Republic of Ireland; Galway University Hospital, Galway, Republic of Ireland.
authors.forename: Anthony
authors.initials: A
authors.lastname: Poles
authors.forename: Marcin J
authors.initials: MJ
authors.lastname: Woźniak
authors.forename: Piers
authors.initials: P
authors.lastname: Walser
authors.forename: Kay
authors.initials: K
authors.lastname: Ridgwell
authors.forename: Joan
authors.initials: J
authors.lastname: Fitzgerald
authors.forename: Ann
authors.initials: A
authors.lastname: Green
authors.forename: Ruth
authors.initials: R
authors.lastname: Gilmore
authors.forename: Geoff
authors.initials: G
authors.lastname: Lucas
mesh_terms: D000328:Adult; D016824:Antigens, Human Platelet / Q000235:genetics / Q000378:metabolism; D018955:CD36 Antigens / Q000235:genetics*; D000939:Epitopes / Q000235:genetics* / Q000276:immunology*; D005091:Exons / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D039421:Integrin alpha2 / Q000235:genetics / Q000378:metabolism; D039661:Integrin beta3 / Q000235:genetics / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D009154:Mutation; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011247:Pregnancy; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000235:genetics* / Q000276:immunology*
chemical_list: D016824:Antigens, Human Platelet; D018955:CD36 Antigens; D000939:Epitopes; C056564:ITGA2B protein, human; C061248:ITGB3 protein, human; D039421:Integrin alpha2; D039661:Integrin beta3