The association between the TCRalphabeta-CD3gammaepsilondeltaepsilon hexamers and zeta2 homodimers in the endoplasmic reticulum (ER) constitutes a key step in TCR assembly and export to the T cell surface. Incompletely assembled TCR-CD3 complexes are degraded in the ER or the lysosomes. A previously described Jurkat variant (J79) has a mutation at position 195 on the TCR Calpha domain causing a phenylalanine to valine exchange. This results in a lack of association between TCRalphabeta-CD3gammaepsilondeltaepsilon hexamers and zeta2 homodimers. Two main hypotheses could explain this phenomenon in J79 cells: TCR-CD3 hexamers may be incapable of interacting with zeta2 due to a structural change in the TCR Calpha region; alternatively, TCR-CD3 hexamers may be incapable of interacting with zeta2 due to factors unrelated to either molecular complex. In order to assess these two possibilities, the TCR-CD3 membrane-negative J79 cells were treated with ethylmethylsulfonate and clones positive for TCR membrane expression were isolated. The characterization of the J79r58 phenotypic revertant cell line is the subject of this study. The main question was to assess the reason for the TCR re-expression. The TCR on J79r58 cells appears qualitatively and functionally equivalent to wild-type TCR complexes. Nucleotide sequence analysis confirmed the presence of the original mutation in the TCR Calpha region but failed to detect compensatory mutations in alpha, beta, gamma, delta, epsilon or zeta chains. Thus, mutated J79-TCR-CD3 complexes can interact with zeta2 homodimers. Possible mechanisms for the unsuccessful TCR-CD3 interaction with zeta2 homodimers are presented and discussed.

The present study was performed in order to analyze whether T‐cell receptor (TCR)/CD3 assembly, intracellular transport and surface expression are carried in a similar way in αβ‐and γδ‐T cells. By means of optimal immunoprecipitation conditions with 35S‐methionine/cysteine‐ or biotin‐labelled TCR/CD3 proteins from αβ‐ or γδ‐T‐lymphoma‐cell lines, as well as TCRγδ cDNA transfectants, it was found that CD3δ chains associate less strongly with TCRγδ heterodimers compared to TCRαβ heterodimers. This preferential reactivity of CD3δ chains appears to be structural and not owing to differences in γδ‐ versus αβ‐T‐cell intracellular environments. Our results are in accordance firstly, with data from CD3δ‐deficient mice, which have γδ‐T cells but no αβ‐T cells, secondly with the suggested role of CD3δ chains in the positive selection of αβ‐T cells, a process apparently not followed by γδ‐T cells, and lastly with the differential roles of CD3δ chains versus CD3γ chains, explaining the maintenance of two CD3δ and CD3γ genes after the duplication from a CD3δ/γ gene present in avians. The impaired reactivity of CD3δ chains with TCRγδ heterodimers seems to be owing to a less efficient association with TCRγ chains. In contrast, CD3δ chains interact as strongly with TCRδ chains as do CD3γ chains with both TCRγ and TCRδ chains. These data may explain, at the molecular levels, why surface TCR/CD3 expression levels are impaired in γδ‐T cells from CD3γ‐deficient mice but not from CD3δ‐deficient mice.

Syngenic C57BL/6 mice (H-2b) vaccinated with mitomycin C-treated L12R4 T lymphoma cells develop protective immunity toward the MHC class II-negative tumor cells. In the present study, we characterize the nature, mode of function, and specificity of the effector cells in this immunity. These cells are TCR-specific CD8+ T lymphocytes with effector function in vitro as well as in vivo upon transfer to naive mice. They produce high levels of IFN-γ and TNF-α, but little or no IL-4. By means of TCRβ-negative variant L12R4 cells, P3.3, and TCR-Vβ2 cDNA-transfected and TCR-Vβ2-expressing P3.3 lymphoma cells, we found that a significant part of the effector T cells are specific for the Vβ12 region. The growth inhibition of L12R4 cells in vitro was inhibited by anti-H-2, anti-Kb, and anti-Db mAb. Furthermore, vaccination with Vβ12 peptide p67–78, which binds to both Kb and Db MHC class I molecules, induces partial protection against L12R4 T lymphoma cells. Thus, self-reactive TCR-Vβ-specific, Kb-, or Db-restricted CD8+ T cells mediate inhibition of T cell lymphoma growth in vitro and in vivo.