Thymic deletion of Vβ11⁺, Vβ5⁺ T cells in H-2E negative, HLA-DQβ⁺ single transgenic mice

DQw6b transgenic mice have been generated by microinjecting a linearized cosmid clone containing 34-kb DQb genomic DNA, isolated from HLA-homozygous B cell line AKIBA (BR2, Dw12, DQw6), into embryos of (CBA x B10.M)F₂ or (SWR x SJL)F₂. Among 85 mice screened, eight mice were transgene-positive. The transgene in seven of eight founders was germline-transmitted. FACS analysis and immunohistochemical studies with DQβ-specific mAb demonstrated that DQβ molecules in association with mouse Aα(f) molecules are expressed on peripheral mononuclear cells, spleen cells, and in thymic medulla. More interestingly, Vβ11-, Vβ5.1-, and Vβ5.2-bearing T cells, but not Vβ8.2-bearing T cells, were clonally deleted in the H-2E-negative but DQβ⁺ progeny of two selected founders (260-23 and 258-10). The deletion was found to take place intrathymically during the transition stage from immature to mature thymocyte development. We postulate that although human DQ genes are more homologous to mouse H-2a genes, Aα(f)/DQβ hybrid molecules may possess the same self-peptide- (or superantigen)-presenting epitope as Eα/Eβ molecules critical for deletion of Vβ11-, Vβ5.1-, and Vβ5.2-bearing T cells in thymus. Our results also confirm the previous findings that accessory molecules on thymocytes such as CD4 may be involved in thymic selection, and further suggest that an interaction of mouse CD4 and mouse Aα chain is required for the clonal deletion.