A new platelet polymorphism Duv(a+), localized within the RGD binding domain of glycoprotein IIIa, is associated with neonatal thrombocytopenia.
We report here the identification and characterization of a new platelet alloantigen, Duv(a+), implicated in a case of neonatal thrombocytopenia. Immunochemical studies demonstrated that the epitope was localized on glycoprotein (GP) IIIa. Sequencing of the exons 2 to 15 of GP IIIa gene polymerase chain reaction products from both parents revealed a single base substitution 517C>T (complementary DNA) present in a heterozygous state in DNA from the father leading to amino acid substitution Thr140Ile (ACC>ATC) within the Arg-Gly-Asp binding domain of GP IIIa. Flow cytometry and immunoprecipitation studies of IIb-C517 or T517 IIIa transfected Cos cells allowed us to demonstrate this mutation was responsible for expression of the Duv(a+) epitope. By polymerase chain reaction-single-strand conformational-polymorphism analysis, the mutated allele could not be detected in a population of 100 healthy unrelated donors, indicating a low frequency of occurrence. The Thr140/Ile dimorphism, localized 3 amino acids upstream from the Arg143 involved in the expression of HPA-4a, did not interfere with the binding of an anti-HPA-4a antibody in flow cytometry. Results of functional analysis of wild-type or mutated transfected CHO cells-(1) aggregation in the presence of Ca(++) and soluble fibrinogen after complex activation by dithiothreitol, (2) adhesion on coated fibrinogen, (3) binding of monoclonal antibody PAC-1 or LIBS antibody D3, and (4) outside-in signaling-all suggest that the Thr140Ile polymorphism localized in the Arg-Gly-Asp binding domain of GP IIIa does not affect significantly, if at all, the integrin function. We have shown that the anti-Duv(a+) antibody may inhibit platelet GP IIb-IIIa function.
Jallu
Vincent
V
Platelet Unit, INTS, Paris, France.
Meunier
Marc
M
Brément
Maryline
M
Kaplan
Cécile
C
D000328:Adult; D019943:Amino Acid Substitution; D015703:Antigens, CD / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D000939:Epitopes / Q000235:genetics; D005192:Family Health; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D039661:Integrin beta3; D016023:Integrins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007519:Isoantigens / Q000097:blood; D008297:Male; D009842:Oligopeptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000502:physiology; D010980:Platelet Membrane Glycoproteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D011110:Polymorphism, Genetic / Q000276:immunology*; D011485:Protein Binding / Q000235:genetics; D013921:Thrombocytopenia / Q000151:congenital* / Q000235:genetics / Q000276:immunology; D014162:Transfection
D015703:Antigens, CD; D000939:Epitopes; D039661:Integrin beta3; D016023:Integrins; D007519:Isoantigens; D009842:Oligopeptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D010980:Platelet Membrane Glycoproteins; C047981:arginyl-glycyl-aspartic acid