Functional polymorphisms among HLA-DR4+ DR beta chains associated with limited peptide diversity

Tryptic peptide map analysis by high-pressure liquid chromatography of DR4- associated DR beta chains revealed limited structural variation within DR beta polypeptides. Comparison of 3H-leucine-labelled tryptic peptide maps of Dw4 and Dw14 homozygous cells identified distinct peaks corresponding to Dw4 and Dw14-associated DR beta polypeptides. HPLC analysis of cell line 256, heterozygous for two DR4-related specificities, Dw4 and Dw14, displayed both peptides, corresponding to the variable Dw4 and Dw14 chromatograms. This observation was confirmed using a deletion mutant cell line derived from 256 lacking Dw4-associated class II genes. The observed peptide variation correlated precisely with predicted nucleotide-derived amino acid sequences implicating amino acids 66-71 of the DR beta chain as contributing to HLA-D structural and functional polymorphisms.