The restricted use of IGHV3 superspecies genes in anti-Rh is not limited to hyperimmunized anti-D donors

BACKGROUND: Antibodies produced against the D antigen make use of IGHV genes restricted to the IGHV3 superfamily. These findings are based on the IGHV gene analysis in anti-D-producing B cells from hyperimmunized donors, however, and therefore the restriction might be due to the hyperimmunization. In this study the IGHV gene usage of anti-Rh-producing B cells in a woman who was immunized in the last trimester of her pregnancy was analyzed. STUDY DESIGN AND METHODS; Serologic analysis was performed by absorption and elution. Antibody-dependent cellular cytotoxicity (ADCC) of the different anti-Rh was determined. A phage display library was constructed from 2.2 x 10(6) isolated B cells and pannings were performed with red cells of the r'r, R1R1, and R2R2 phenotype. RESULTS: A plasma sample of the immunized person showed high levels of both anti-D and anti-G and low levels of anti-C. Anti-D and anti-G contributed equally strong to the ADCC whereas anti-C did not. Eighteen anti-D-, 5 anti-G-, and 1 anti-C-specific phage clones were found, of which 16, 2, and 1 used the IGHV3s genes, respectively. CONCLUSION: For the first time a restriction to the IGHV3s genes in anti-D in a naturally immunized pregnant woman is shown. Moreover, the use of IGHV3s genes appears to be present in anti-C and anti-G as well. Therefore, it is concluded that restricted IGHV3s gene usage in anti-D is not due to hyperimmunization but due to characteristics of the Rh antigens and the intrinsic binding capacities of IGHV3s genes, supporting the common Rh footprint hypothesis.