Murine monoclonal antibodies reactive with a human monoclonal anti‐RhD antibody (BRAD‐5)

BRAD‐3 and BRAD‐5 are human monoclonal antibodies that recognize the RhD antigen on red blood cells. Both antibodies are currently in clinical trials for use as a replacement for polyclonal anti‐RhD in the prophylactic treatment of haemolytic disease of the newborn. We have produced three murine IgG1 antibodies that cause agglutination of cells sensitized with BRAD‐5 and also block binding of BRAD‐5 to its target antigen. Using a haemagglutination assay, these antibodies, 1D7, 2E6 and 3B1, have shown specificity for BRAD‐5 as they did not bind to other monoclonal anti‐RhD antibodies of differing specificity or derived from other donors. This assay has also been used to show a lack of reactivity with anti‐RhD antibodies present in 198 human serum samples from 44 anti‐RhD immune individuals. The three anti‐BRAD‐5 antibodies have been shown to recognize different epitopes on the BRAD‐5 molecule using a blocking ELISA. These antibodies appear to recognize private idiotopes on BRAD‐5 that were not detectable in RhD immune sera, and therefore they will be of use for monitoring BRAD‐5 in clinical trials.