Comparison of the peptide composition of two histocompatibility-2 alloantigens.

The peptide composition of purified Histocompatibility-2 (H-2) reactive glycoprotein fragments from two murine strains allelic at the H-2 locus (H-2(b) and H-2(d)) were compared by a cellulose thin-layer peptide mapping micro technique. Approximately 70 per cent of the theoretical maximum number of peptides produced by cyanogen bromide cleavage and trypsin digestion were visualized by this technique. Most (38) of the peptides for the glycoproteins from these strains allelic for the H-2 locus were identical; however, three peptides of the H-2(b) and four peptides of the H-2(d) alloantigen were unique. The results demonstrate the remarkable similarity in protein structure between these two allelic products, but also show a small but reproducible difference in their peptide composition. The findings are consistent with the hypothesis that protein primary structure may determine wholly or in part their alloantigenic activities.