New low-frequency platelet glycoprotein polymorphisms associated with neonatal alloimmune thrombocytopenia.
BACKGROUND
Recent reports suggest that maternal immunization against low-frequency, platelet (PLT)-specific glycoprotein (GP) polymorphisms is a more common cause of neonatal alloimmune thrombocytopenia (NATP) than previously thought.


METHODS
Serologic and molecular studies were performed on PLTs and DNA from three families in which an infant was born with apparent NATP not attributable to maternal immunization against known PLT-specific alloantigens.


RESULTS
Antibodies reactive only with paternal PLTs were identified in each mother. In Cases 2 (Kno) and 3 (Nos), but not Case 1 (Sta), antibody recognized paternal GPIIb/IIIa in solid-phase assays. Unique mutations encoding amino acid substitutions in GPIIb (Case 2) or GPIIIa (Cases 1 and 3) were identified in paternal DNA and in DNA from two of the affected infants. Antibody from all three cases recognized recombinant GPIIIa (Case 1 [Sta] and Case 3 [Nos]) and GPIIb (Case 2, Kno) mutated to contain the polymorphisms identified in the respective fathers. None of 100 unselected normal subjects possessed the paternal mutations. Enzyme-linked immunosorbent assay and flow cytometric studies suggested that failure of maternal serum from Case 1 (Sta) to react with paternal GPIIIa in solid-phase assays resulted from use of a monoclonal antibody AP2, for antigen immobilization that competed with the maternal antibody for binding to the Sta epitope.


CONCLUSIONS
NATP in the three cases was caused by maternal immunization against previously unreported, low-frequency GP polymorphisms. Maternal immunization against low-frequency PLT-specific alloantigens should be considered in cases of apparent NATP not resolved by conventional serologic and molecular testing.
Peterson
Julie A
JA
Blood Research Institute and Platelet & Neutrophil Immunology Laboratory, BloodCenter of Wisconsin, Milwaukee, Wisconsin 53201-2178, USA. julie.peterson@bcw.edu
Gitter
Maria L
ML
Kanack
Adam
A
Curtis
Brian
B
McFarland
Janice
J
Bougie
Daniel
D
Aster
Richard
R
D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D016824:Antigens, Human Platelet / Q000235:genetics* / Q000276:immunology; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005260:Female; D005787:Gene Frequency; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007231:Infant, Newborn; D039421:Integrin alpha2 / Q000235:genetics* / Q000276:immunology; D039661:Integrin beta3 / Q000235:genetics* / Q000276:immunology; D007518:Isoantibodies / Q000276:immunology; D008297:Male; D008431:Maternal-Fetal Exchange; D008958:Models, Molecular; D011110:Polymorphism, Genetic; D011247:Pregnancy; D011993:Recombinant Fusion Proteins / Q000276:immunology; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000235:genetics* / Q000276:immunology
D000911:Antibodies, Monoclonal; D016824:Antigens, Human Platelet; D000939:Epitopes; C056564:ITGA2B protein, human; C061248:ITGB3 protein, human; D007074:Immunoglobulin G; D039421:Integrin alpha2; D039661:Integrin beta3; D007518:Isoantibodies; D011993:Recombinant Fusion Proteins