The thymus leukemia antigens (TL) belong to the MHC class Ib family and can be recognized by CD8-dependent or -independent cytotoxic T lymphocytes (CTL) showing TL, but not H-2, restriction. We previously reported that the CTL epitope is TAP independent and in the present study we further characterize the recognition mechanism of CD8-dependent TL-specific TCRαβ CTL. We first prepared empty TL tetramers by way of peptide-independent folding with recombinant proteins produced in an Escherichia coli expression system, and showed that TL-specific CTL recognized TL without putative TL-associated peptide and/or post-translational modifications of TL by mammalian and insect cells. We next prepared transfectants expressing various chimeric TL molecules with mouse or human MHC class I as well as chimeric TL tetramers with recombinant proteins produced by insect cells, and demonstrated that chimeric TL whose α3 domain was replaced by that of H-2Kb, but not of HLA-A2, was sufficient for binding and activation of TL-specific CTL. These results indicate that TL-specific CTL recognize predominantly their α1/α2 domain as an epitope(s) and that the binding activity to the murine CD8 of the α3 domain of H-2Kb is sufficient to induce their CTL activity, although it is known to be weaker than that of TL, but stronger than that of HLA. The results taken together indicate that CD8-dependent TL-specific TCRαβ CTL recognize an epitope(s) of the α1/α2 domain of TL free from antigenic molecules, and that CD8 plays an important role in stable interactions between TL and their corresponding TCR.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy