Persistent anti-Dr^a in two pregnancies

The Drori (Dr^a) antigen is one of the ten high-prevalence antigens of the Cromer blood system, which are carried on decay-accelerating factor (DAF, CD55). The Dr(a–) phenotype was first described in a 48-year-old Jewish woman from Bukhara. Her serum contained an antibody to a high-prevalence antigen named anti-Dr^a. Most known individuals with the Dr(a–) phenotype are Jews from the geographic area of Bukhara, but individuals from Japan have also been described. Antibodies in the Cromer blood group system, including anti-Dr^a, have never been reported to cause HDN. In most of the cases with anti-Dr^a examined in Israel, the antibodies have been subtyped as IgG2 and IgG4. This report is of a woman with Dr(a–) phenotype and an anti-Dr^a titer of 256 to 512 in her serum, observed during two successive pregnancies. At birth, the RBCs of the first- and second-born child were negative and positive in the DAT, respectively, and neither manifested clinical signs of HDN. The disappearance of Cromer system antibodies, including anti-Dr^a in midpregnancy, has been described in a previous study. In that study, it was theorized that the antibodies in the serum of the women were adsorbed onto placental DAF. The finding of a high anti-Dr^a titer in two successive pregnancies in this patient, with a positive DAT for the RBCs of one of the two babies at term, differs from published reports, suggesting that a different mechanism might be involved. Immunohematology2005;21:126–128.