Human monoclonal anti-Rh antibodies produced by human-mouse heterohybridomas express the Gal alpha 1-3 Gal epitope.

The presence of the Gal alpha 1-3 Gal structure (Gal epitope) in the carbohydrate component of fifteen human monoclonal antibodies with specificity for the Rh blood group factor and produced by human-mouse heterohybridomas was evaluated. To do that, an antiglobulin-like agglutination test and an enzyme linked immunosorbent assay were performed using an affinity-purified anti-Gal antibody obtained from the serum of an AB blood group donor. Using the antiglobulin reaction, results were obtained showing that only five of the fifteen human monoclonal antibodies tested contained the structure at levels sufficient to allow agglutination. However, all fifteen monoclonals were positive using the more sensitive enzyme linked immunosorbent assay. By means of an indirect immunofluorescence assay the same anti-Gal antibody was used to test the presence of Gal epitopes on the surface of the producer heterohybridomas. Results were obtained indicating that twelve out of the fifteen hybridomas studied do express the Gal structure on its surface. The relevance of these findings is discussed in the context of therapeutic applications of human monoclonal antibodies.