Chemical typing of human immunoglobulin VH subgroups

Abstract A simple method is defined, that describes a chemical way of typing for the human V H subgroups, which relies on the separation of peptides characteristics of each of the V H I, V H II and V H III basic sequences by high voltage electrophoresis on paper in one single dimension at pH 6·5. Peptides were obtained from heavy chains that had been fully reduced and carboxymethylated with 14 C-iodoacetic acid, and were detected by autoradiography. Specific peptides that provided the basis for V H identification contained the first cysteyl residue (C 1 ) of the heavy chains and a methionyl residue characteristic of the V H II sequences. The method allowed a re-estimation of the relative contribution of the V H I, V H II and V H III subgroups to the normal IgG pool. A fairly large amount of blocked heavy chains was unequivocally assigned to the V H III subgroups which leads to a decrease of the previously reported V H I/V H III ratio.