A bicarbonate anion-dependent anti-’N’ MoAb

While studying the serologic characteristics of certain monoclonal blood group antibodies, we observed a hybridoma clone (5A- 11E10) with anti-N–like serologic specificity that was dependent on the presence of the bicarbonate anion. The diluted cell culture supernatant preferentially agglutinated M–N+ RBCs by immediate spin. This supernatant also agglutinated M–N+ RBCs that had been treated with trypsin or sialidase (to remove N-reactivity), suggesting anti-’N’ activity. Anti-’N’ specificity was confirmed by the supernatant’s non-reactivity with N+ RBCs treated with papain (to remove ‘N’ reactivity) or with (‘N’-negative) M+N–U– RBCs. The requirement for bicarbonate in the MoAb’s formulation was not a function of pH. Both sodium and ammonium bicarbonate supported agglutination, but neither sulfate nor carbonate was effective.