Cells homozygous for two HLA-DR7-associated HLA-D specificities express highly similar DR molecules but different DQ molecules.

The Ia molecules expressed by cells homozygous for two distinct HLA-DR7-associated HLA-D specificities, Dw7S and Dw11L, were compared. The complete Ia phenotypes of these cells are DR7, DRw53, DQw2, Dw7S, DPw4 and DR7, DRw53, DQw3, Dw11L, DPw4, respectively. Immunofluorescence analysis revealed that three DQ-specific monoclonal antibodies (Leu-10, 33.1, and HK-19), which detect polymorphic DQ determinants that do not correspond to known serologic specificities, are nonreactive with DR7, Dw7S cells but are reactive with DR7, Dw11L cells. The DR molecules isolated from Dw7S and Dw11L cells are very similar and comigrate when analyzed together by two-dimensional gel electrophoresis. In contrast, the DQ molecules isolated from these cells are structurally distinct: the DQ beta chains of DQw2-bearing molecules from Dw7S cells are very basic, while those of DQw3-bearing DQ molecules from Dw11L cells are more acidic. The finding that two DR7, D-different cells express indistinguishable DR molecules and structurally distinct DQ molecules documents a unique pattern of Ia molecular organization which is different from those previously described for the DR2-, DR4-, or DRw8-associated HLA-D specificities.