Two Ig framework I epitopic specificities recognized by a rabbit antiserum and a monoclonal antibody to mouse VH chains.

The reactivity of 23 mouse monoclonal Ig with a rabbit polyclonal antiserum to VH of anti-alpha(1----6)dextran 19.22.1 and with a monoclonal anti-VH of anti-DNP MOPC315, when correlated with amino acid sequence, identified several residues in the first and third framework regions as being of potential importance in forming the epitope. Inhibition studies using synthetic peptides corresponding to residues 1-15 of the monoclonal Ig used to produce the poly- and monoclonal reagents provide evidence that the epitopes are predominantly, if not exclusively, specific for the N-terminal strand of the domain. Examination of known x-ray structures of mouse VH suggests that the primary difference between the two epitopes in the N-terminal strands is determined by the peptide chain structure due to Pro at position 9. Pro 9 appears essential for the epitope reactive with anti-VH MOPC315.