Murine monoclonal antibody with anti‐e‐like specificity: suitability for screening for e‐negative cells

A directly agglutinating murine monoclonal antibody of the IgG3 isotype has been produced after mice were immunized with papain-treated Bombay phenotype, e-positive red cells (RBCs). The antibody strongly agglutinated all e-positive RBCs and gave negative reactions with RBCs from Rhnull persons and those homozygous for Rh deletion genes. Variable reactivity was found with e-negative RBCs, ranging from weak to negative with R2R2, slightly stronger with r"r", and stronger still with RzRz. These reactions, together with results from tests with a large panel of Rh-variant RBCs, suggested a specificity for an epitope that is part of the e mosaic but is also expressed at least partially on e-negative RBCs and is influenced by the presence of C. This antibody has been standardized for use as a screening reagent for R2R2 cells by a microplate technique, and over 6000 donations have been screened in this way. No discrepancies have been found in confirmatory tests for e-negative status using human anti-e.