IMMUNE RECOGNITION OF HUMAN COLONIC-TUMOR-ASSOCIATED MUC-2 MUCINS USING AN ANTIPEPTIDE ANTIBODY

In human intestinal malignancy, alterations occur in the expression of mucins defined by the MUC-2 gene. These changes include the unmasking of epitopes in the mucin protein core. In order to probe these modifi cations associated with mucins of the malignant phenotype, a monoclona l antibody (MAb) was developed against synthetic peptide with a sequen ce based upon that of the protein core of the MUC-2 mucin. The antibod y (designated 996) was shown to recognize a high-molecular-weight glyc oprotein from colonic carcinoma tissue. The material reacted uniformly with Concanavalin A but variably with other lectins, indicating heter ogeneity in the associated oligosaccharide side chains. The protein co re was accessible both to 996 antibody binding and to degradation with proteases. Immunization with the affinity-purified mucin-like materia l elicited antibodies reactive with both the immunogen and the synthet ic peptides, confirming the immunogenic character of protein-core dete rminants. Epitope mapping studies, using synthetic peptides in solutio n and synthetic peptides tethered to the heads of plastic pins, indica ted that the minimum epitope for the 996 antibody is a tetramer of T G T Q. Antibody interaction with the glutamine (Q) residue was determin ed to be of major importance in the antigen-antibody reaction. The fin dings illustrate the characterization of an anti-peptide antibody whic h may be used to probe alterations in MUC-2 mucin expression associate d with human intestinal malignant disease. (C) 1993 Wiley-Liss, Inc.