Investigations using a novel monoclonal antibody to the glycosylphosphatidylinositol‐anchored protein that carries Gregory, Holley, and Dombrock blood group antigens

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Abstract
BACKGROUND: The high‐frequency Hy and Gya antigens have been shown to reside on the same protein. Gy(a‐) Hy‐negative red cells are also Do(a‐ b‐). A mouse monoclonal antibody, 5B10, was produced with specificity related to the human Gregory, Holley, and Dombrock blood group antigens. STUDY DESIGN AND METHODS: The antibody reacted in direct hemagglutination assays, and its specificity was investigated by radioimmunoassay, inhibition assay, and Western blotting. RESULTS: The 5B10 antibody failed to bind to abnormal paroxysmal nocturnal hemoglobinuria red cells and human erythroleukemia cell line K562, but it was weakly reactive with HEL cells. Red cells, but not other circulating hematopoietic cells, express the 5B10 antigen. The 5B10 antibody had a specificity similar but not identical to that of Gya. Gy(a‐) Hy‐negative red cells reacted extremely weakly with 5B10 antibody, but Gy(a‐) Hy‐negative red cells treated with a variety of proteases bound 5B10 antibody strongly. This suggests that these cells express a variant form of the protein recognized by 5B10. CONCLUSION: Identification of a monoclonal antibody to this glycosylphosphatidylinositol‐linked protein opens a new avenue for investigation of the biochemistry, genetics, and function of the glycosylphosphatidylinositol‐linked protein that bears the Gya, Hy, and Do antigens.