Immunochemical analysis of the Ia polymorphisms among the family of DR7-associated HLA-D specificities

Among cells that bear the serologically defined Ia alloantigen DR7, four T cell-defined HLA-D specificities have been described: Dw7, Dw17, Dw11, and Dw7L. Ia molecules expressed by cells homozygous for these specificities have been compared by using immunofluorescence and two-dimensional gel electrophoresis in order to identify the DR and DQ polymorphisms among the family of DR7-associated HLA-D specificities. Cells homozygous for each of the four HLA-D specificities have in common one DR molecule that is indistinguishable by these methods. Two DR-specific monoclonal antibodies, IIIE3 and 109d6, detect a second distinct DR molecule on Dw7, Dw17, and Dw7L cells. This second DR molecule is also very similar from cells of the three specificities. In contrast, a second DR molecule was not detected on four Dw11 homozygous cells. Therefore, these data raise the possibility that all DR homozygous cells do not express the same number of DR molecules. The DQ molecules expressed by DQw2-positive Dw7, Dw17, and Dw7L cells are also very similar, whereas DQw3-positive Dw11 DQ molecules are structurally different. Therefore, no DR or DQ structural polymorphisms were detected to correlate with the Dw7, Dw17, and Dw7L T cell-defined Ia polymorphisms.