Partial N-terminal sequence analysis of human class II molecules expressing the DQw3 determinant

Abstract

HLA-DQ molecules were isolated from DRw9-homozygous and DR4-homozygous cell lines by using a monoclonal antibody HU-18, which recognizes class II molecules carrying the conventional DQw3 determinant. The partial N-terminal sequence analysis of the DQw3 molecules revealed that they have sequences homologous to those of murine I-A molecules. Within the limits of our sequence analysis, the DQw3 molecules from the two cell lines are identical to each other in both the α and β chains. The DQα as well as DQβ chains were found to have amino acid substitution when compared to other I-A-like molecules whose sequences have been reported. These differences may contribute to the DQw supertypic specificity. The polymorphic nature of DQ molecules is in marked contrast to that of DR molecules where DRα chains are highly conserved while DRβ chains have easily detectable amino acid substitutions.