Persistent anti-Dra in two pregnancies.

Area of Science:

• Immunology
• Hematology
• Genetics

Background:

• The Drori (Dr(a)) antigen is a high-prevalence antigen on decay-accelerating factor (DAF, CD55) within the Cromer blood group system.
• The Dr(a-) phenotype is rare, predominantly found in individuals of Jewish Bukhara or Japanese descent.
• Cromer blood group system antibodies, including anti-Dr(a), have not been previously associated with hemolytic disease of the newborn (HDN).

Purpose of the Study:

• To report a case of a woman with the Dr(a-) phenotype experiencing high anti-Dr(a) antibody titers during two pregnancies.
• To investigate the clinical implications and potential mechanisms behind the observed high antibody titers in the absence of HDN.

Main Methods:

• Case report detailing serological findings during two successive pregnancies.
• Analysis of anti-Dr(a) antibody titers and direct antiglobulin test (DAT) results in mother and neonates.
• Review of existing literature on Cromer blood group system antibodies and HDN.

Main Results:

• The patient presented with high anti-Dr(a) antibody titers (256-512) in both pregnancies.
• The first infant's red blood cells (RBCs) were DAT-negative, while the second infant's RBCs were DAT-positive at birth.
• Neither infant exhibited clinical signs of HDN, despite the DAT-positive result in the second infant.

Conclusions:

• The high anti-Dr(a) titers observed in this case, coupled with the absence of HDN, challenge previous understanding of this antibody's clinical significance.
• The findings suggest a potential mechanism, distinct from previously theorized placental adsorption, that protects against HDN in this specific context.
• Further research is warranted to elucidate the protective factors and immunological mechanisms involved.