[Structural analysis of DR and DQ molecules among three HLA-D clusters associated with HLA-DR4]

In this study, the DR and DQ molecules from three different HLA-D clusters; HLA-Dw4, DKT2, and Dw15, associated with HLA-DR4 were analysed using monoclonal antibodies and two-dimensional gel electrophoresis. The results of serological analyses of specificity, sequential coprecipitation assays, and two-dimensional gel analyses showed that two monoclonal antibodies, HU-18 and HU-23 recognize two distinct antigenic epitopes borne on DQw3 molecules. In two-dimensional gel analysis, the DR4 light chains from ER (DR4, DQw3, Dw4 homozygous), KT2 (DR4, DQw3, DKT2 homozygous), and EBV-Wa (DR4, DQ--, Dw15 homozygous) cells were clearly different from each other in terms of their isoelectric points. Similary, the DQw3 light chains from ER and KT2 cells were also electrophoretically different. Moreover, it was indicated that DQw3 molecules from four different B cell lines being typed in a single cluster of HLA-Dw4 specificity differ in the serological reactivity with HU-23. These results suggested that DR molecules are the major component participating in the determination of the HLA-D specificity.