Anti-HrB and anti-hrb revisited.

BACKGROUND: Since their description in the 1970s, anti-HrB (antibody against a high-prevalence Rh antigen) and anti-hrB (anti-e–like antibody) are still a subject of debate about representing two aspects of a global immune response or being two independent antibodies. STUDY DESIGN AND METHODS: The aim of this study was to evaluate the immune response against the antigens of Rh system of 30 individuals presenting a hrB(RH31)− phenotype. Genomic analysis of RH genes was performed in all individuals. RESULTS: Among the 30 individuals, 27 had a HrB(RH34)− phenotype. No immunization against Rh antigens was found in 16 individuals. Three individuals made anti-D only, whereas six individuals made anti-HrB (four with anti-hrB and two without anti-hrB) and two individuals made anti-hrB without anti-HrB. Among the 30 individuals, three had a HrB+ phenotype. No immunization against Rh antigens was found in one individual, whereas two individuals made anti-hrB; the genomic analysis of selected individuals showed the presence of a (C)ces haplotype, either Type 1 or Type 2, and a DIII Type 5 ces haplotype, in the homozygous state, in compound heterozygosity with each other or in heterozygosity with a DcE haplotype. Genomic data were in accordance with serologic data. CONCLUSION: Our data provide the evidence that anti-HrB and anti-hrB are independent antibodies, defining two different specificities. These antibodies may be produced by individuals expressing variants of RhCE protein. Serologic and molecular data indicate that e antigen encoded by the (C)ces haplotype is a partial antigen. In individuals carrying a (C)ces haplotype, the risk and the type of alloimmunization to Rh antigens are related to the second Rh haplotype.