Anti-HrB and anti-hrb revisited

Since their description in the 1970s, anti-Hr(B) (antibody against a high-prevalence Rh antigen) and anti-hr(B) (anti-e-like antibody) are still a subject of debate about representing two aspects of a global immune response or being two independent antibodies.

The aim of this study was to evaluate the immune response against the antigens of Rh system of 30 individuals presenting a hr(B)(RH31)- phenotype. Genomic analysis of RH genes was performed in all individuals.

Among the 30 individuals, 27 had a Hr(B)(RH34)- phenotype. No immunization against Rh antigens was found in 16 individuals. Three individuals made anti-D only, whereas six individuals made anti-Hr(B) (four with anti-hr(B) and two without anti-hr(B)) and two individuals made anti-hr(B) without anti-Hr(B). Among the 30 individuals, three had a Hr(B)+ phenotype. No immunization against Rh antigens was found in one individual, whereas two individuals made anti-hr(B); the genomic analysis of selected individuals showed the presence of a (C)ce(s) haplotype, either Type 1 or Type 2, and a DIII Type 5 ce(s) 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.

Our data provide the evidence that anti-Hr(B) and anti-hr(B) 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)ce(s) haplotype is a partial antigen. In individuals carrying a (C)ce(s) haplotype, the risk and the type of alloimmunization to Rh antigens are related to the second Rh haplotype.