Neonatal alloimmune thrombocytopenia associated with maternal-fetal incompatibility for blood group B.
BACKGROUND
Blood group A and B antigens are expressed only weakly on platelets (PLTs) of most individuals but are very strongly expressed on PLTs from approximately 1 percent of normal subjects (Type II high expressers). The implications of this trait for transfusion medicine are undefined.


METHODS
A family was studied in which two Group B infants were born with neonatal thrombocytopenia, whereas a third infant whose blood group was A(2) had a normal PLT count at birth.


RESULTS
Serologic studies demonstrated a maternal antibody that reacted strongly with PLTs from the father and the two group B children in flow cytometry and with GPIIb/IIIa from their PLTs in solid-phase assays. No PLT-specific antibodies were detected in maternal serum sample, but it contained a high-titer immunoglobulin G antibody specific for blood group B. All PLT-reactive antibody in the mother's serum was removed by absorption with pooled, washed group A and B red cells (RBCs). Studies with monoclonal anti-B and measurement of serum B-glycosyltransferase activity showed that the father and both group B children were Type II high expressers of blood group B.


CONCLUSIONS
The findings indicate that high-titer blood group antibodies acquired from the mother can cause thrombocytopenia in infants possessing the Type II high-expresser phenotype despite competition for antibody binding by blood group antigens expressed on RBCs and other tissues.
Curtis
Brian R
BR
Platelet & Neutrophil Immunology Laboratory, BloodCenter of Wisconsin, Milwaukee, WI 53201-2178, USA. brian.curtis@bcw.edu
Fick
Andrea
A
Lochowicz
Andrew J
AJ
McFarland
Janice G
JG
Ball
Robert H
RH
Peterson
Julie
J
Aster
Richard H
RH
D000017:ABO Blood-Group System / Q000097:blood* / Q000276:immunology*; D000906:Antibodies / Q000276:immunology; D001787:Blood Group Incompatibility / Q000097:blood* / Q000150:complications / Q000276:immunology*; D002648:Child; D005220:Fathers; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007519:Isoantigens / Q000276:immunology; D008297:Male; D008431:Maternal-Fetal Exchange; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology; D011247:Pregnancy; D012680:Sensitivity and Specificity; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000097:blood* / Q000276:immunology*
D000017:ABO Blood-Group System; D000906:Antibodies; D007519:Isoantigens; D019039:Platelet Glycoprotein GPIIb-IIIa Complex