The Bra/Brb alloantigen system on human platelets
V Kiefel, S Santoso, B Katzmann and C Mueller-Eckhardt
Institute for Clinical Immunology, Justus-Liebig-University, Giessen,
Federal Republic of Germany.
Anti-Bra was first identified in four cases of neonatal alloimmune
thrombocytopenia (NAIT). The antigen Bra is localized on the glycoprotein
Ia/IIa complex of platelets. Anti-Bra can best be detected by a
glycoprotein-specific immunoassay using monoclonal antibodies for antigen
immobilization (MAIPA assay) and radioimmunoprecipitation (RIP). Recently,
we have identified sera from two polytransfused patients that contain an
antibody that recognizes Brb, the allele of Bra. Family studies show that
both antigens are inherited as autosomal codominant characters. The gene
frequency of the new allele Brb is 0.888. Approximately 2,000 anti-Bra
binding sites are present on homozygous platelets and 1,000 on heterozygous
platelets. Our findings provide evidence for the first polymorphism
observed on the glycoprotein Ia/IIa complex. Immunization against these
alloantigens is implicated in NAIT and poly-transfused patients.
Volume 73,
Issue 8,
pp. 2219-2223,
06/01/1989
Copyright © 1989 by The American Society of Hematology