Analysis of the specificity of five murine anti-blood group A monoclonal antibodies, including one that identifies type 3 and type 4 A determinants.

The specificity of five mouse monoclonal anti-A blood group antibodies (Ab), four of which were produced by immunization with cultured human cancer cells and one with a synthetic antigen, has been determined by examining their reactivity with purified A glycolipids, erythrocyte glycolipids, oligosaccharides, ovarian cyst glycoproteins, and salivary glycoproteins. Two of the antibodies (HT29-36 and CB) reacted with all A variant structures tested and have a broad anti-A reactivity. Ab CLH6 did not agglutinate A erythrocytes and reacted preferentially with the type 1A structure. Ab S12 agglutinated all A1 erythrocytes and reacted best with simple, monofucosyl type 2 A structures, such as Aa-2, Ab-2, and A tetrasaccharide. Ab M2 has a novel, but complex, spectrum of reactivity. It reacts with type 3 and type 4 A chains and not with type 1 and type 2 A chains. It appears to recognize both an external A structure (formula; see text) (I) (found) in type 3 and type 4 chains) and also an internal structure (II) found in type 3 chains. Ab M2 agglutinates all A and AB erythrocytes but does not react with salivary glycoproteins.