Disappearance of antibodies to Cromer blood group system antigens during mid pregnancy

The Cromer blood group system consists of 7 high incidence and 3 low incidence antigens that are carried on the complement regulatory glycoprotein called decay-accelerating factor (DAF; CD55). Despite laboratory results that would predict clinical significance, antibodies with specificities in the Cromer blood group system have not been reported to cause hemolytic disease of the newborn. It is possible that strong expression of DAF on the apical surface of antigen-positive fetally derived placental trophoblasts may absorb maternal antibodies that are directed to antigens in the Cromer blood group system. We studied two cases where strongly reactive anti-Cra and anti-Dra became undetectable during second and third trimesters of pregnancies.