N-terminal amino acid sequences of the alpha and beta chains of HLA-DR1 and HLA-DR2 antigens.

The N-terminal amino acid sequences of the alpha and beta chains of HLA-DR1 and HLA-DR2 antigens were obtained with subnanomole quantities of material by using a gas-liquid solid-phase sequencer. A comparison of the N-terminal amino acid sequences of HLA-DR1 and HLA-DR2 alpha chains revealed no differences. However, in the first 35 N-terminal residues of the beta chains from HLA-DR1 and HLA-DR2 antigens, two regions of variability are readily apparent, each comprising about six amino acids. Conceivably one or both of these variability regions may be responsible for the serologically defined polymorphism of HLA-DR alloantigens.