Immune induction by a protein antigen and by a peptide segment of the protein.

The immune induction by a protein (the tobacco mosaic virus protein-TMVP) was compared to the immune induction by the free, non-conjugated eicosa tryptic peptide fragment of the protein (tryptic peptide 8 representing residues 93-112 of the protein). The results demonstrated that like TMVP, peptide 8 was immunogenic in A/J mice. TMVP and peptide 8 do not cross react on the T cell level. However, immunization with TMVP or with peptide 8 induces antibodies which react with both TMVP and peptide 8. Characterization of the antibodies produced by both immunogens revealed that: their isotope composition is similar with IgG1 and IgG2 being the predominant isotypes; this composition indicates that both immunogens are T cell dependent antigens, the antibodies induced by TMVP and by peptide 8 are directed against the C-terminal decapeptide portion of peptide 8 (residues 103-112 of the protein), the fine specificity of these antibodies is the same. These results, and results of adoptive transfer experiments, indicate that antigen specific T cells had no effect on the expression of the fine antibody specificity. The results demonstrate the feasibility of immunizing with a portion of a protein for the purpose of inducing antibodies with the same isotype composition and specificity towards a protein epitope as those induced by immunization with the whole protein.