title: Low-frequency human platelet antigens as triggers for neonatal alloimmune thrombocytopenia.
abstract: BACKGROUND
  Twenty-four low-frequency human platelet antigens (LFHPAs) have been implicated as immunogens in neonatal alloimmune thrombocytopenia (NAIT). We performed studies to define more fully how often these antigens trigger maternal immunization leading to NAIT.
  
  
  METHODS
  In a Phase 1 study, fathers of selected NAIT cases not resolved by serologic testing but thought to have a high likelihood of NAIT on clinical and serologic grounds were typed for LFHPAs by DNA sequencing. In a Phase 2 study, high-throughput methods were used to type fathers of 1067 consecutive unresolved NAIT cases for LFHPAs. Mothers of 1338 unresolved cases were also typed to assess the prevalence of LFHPAs in a population racially/ethnically similar to the fathers.
  
  
  RESULTS
  In Phase 1, LFHPAs were identified in 16 of 244 fathers (6.55%). In Phase 2, LFPAs were found in only 28 of 1067 fathers (2.62%). LFHPAs were identified in 27 of 1338 maternal samples (2.01%). HPA-9bw was by far the most common LFHPA identified in the populations studied and was the only LFHPA that was significantly more common in fathers than in mothers of affected infants (p = 0.02).
  
  
  CONCLUSIONS
  Maternal immunization against recognized LFHPAs accounts for only a small fraction of the cases of apparent NAIT not resolved by standard serologic testing. Typing of the fathers of such cases for LFHPAs is likely to be rewarding only when a maternal antibody specific for a paternal platelet glycoprotein is demonstrated and/or there is compelling clinical evidence for NAIT.
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Peterson
authors.forename: Maria
authors.initials: M
authors.lastname: Gitter
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Bougie
authors.forename: Shannon
authors.initials: S
authors.lastname: Pechauer
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Hopp
authors.forename: Brad
authors.initials: B
authors.lastname: Pietz
authors.forename: Aniko
authors.initials: A
authors.lastname: Szabo
authors.forename: Brian R
authors.initials: BR
authors.lastname: Curtis
authors.forename: Janice
authors.initials: J
authors.lastname: McFarland
authors.forename: Richard H
authors.initials: RH
authors.lastname: Aster
mesh_terms: D000483:Alleles; D016824:Antigens, Human Platelet / Q000235:genetics*; D005260:Female; D057166:High-Throughput Screening Assays; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000209:etiology*
chemical_list: D016824:Antigens, Human Platelet