Monoclonal antibody BA-1 to the human B lymphocyte marker CD24 recognizes a sialic acid (N-acetylneuraminic acid) dependent epitope in multi-valent display on peptide

Abstract

SUMMARY Evidence is presented that monoclonal antibody BA-1, directed against a marker (CD24) of human lymphocytes of B cell lineage, recognizes a sialic aeul-dependent cpitopc. This conclusion is based on a scries of experiments exploiting the reaction of this antibody with bovine and ovine submaxillary mucins. Expression of the cpitopc was enhanced following alkaline saponification of bovine submaxillary mucin, which converts 0-acctylatcd ncuraminic acid residues to N-acelylncuraminic acid. The epitope was destroyed following ncuraminidase or mild acid treatment of the mucins, and its expression was diminished following neuraminidasc treatment of B lymphobtastoid cells. Glycopcptidcs obtained by digestion of the bovine mucin with papain, trypsin or pronasc were lacking in antigenicity. However, anligcnic activity could be regenerated after conjugation of pronase glycopepiides to poly-L-lysinc. These results indicate that multivalenl display of sialo-oligosacchar-ide on peptide rather than a protease-susceptible polypcplide domain is required for BA-1 antibody binding.