T-cell dependency of the antibody response to free small synthetic peptides of a protein: demonstration with an antigenic site of myoglobin.

Recent studies from this laboratory have found that synthetic peptides of proteins, as small as 6 residues, when administered in their free form (i.e. without coupling to any carrier) elicit the formation of antibodies with submolecular binding specificities to preselected protein regions. These peptides could represent either the antigenic sites of the protein or surface regions that are not immunogenic when the intact protein is the antigen. In either case the antibodies bind specifically to the intact protein, exclusively at the region used in immunization. In the present study we immunized BALb/c.ByJ and nude (BALb/c derived) strain mice with either Mb or synthetic antigenic site 5 of Mb. Radioimmune antibody binding studies showed that immunization of BALb/c.ByJ strain mice with either Mb or synthetic peptide resulted in the formation of antibodies that bound specifically to Mb, whereas nude mice did not produce such antibodies. These results indicate that the antibody response to both Mb and synthetic antigenic site is T-cell dependent.