Peptide map comparisons of similar serologically defined HLA-DR antigens isolated from different lymphoblastoid cell lines.

In these studies, we have examined the possibility that DR subtypes, closely related to each other in structure, compose the major DR allotypic groups. The structures of DR molecules, isolated from pairs of cell lines that had the same serologically defined HLA-DR type, were compared by peptide mapping. HLA-DR molecules isolated from pairs of cell lines in which both members were either DR1, DR2, or DR7 were identical. However, DR molecules isolated from cell lines LG-29 (DR5) and LG-38 (DR5) displayed two distinct differences in their small (beta) subunits. This number of differences, two of 15 peptides or 15%, is much fewer than is observed between DR allotypes (approximately 50%) and suggests that at least two subtypes exist within the DR5 allotype family.