Despite substantial advances in our understanding of CD4(+)CD25(+) regulatoryT cells, a possible equivalent regulatory subset within the CD8(+) T cell population has received less attention. We now describe novel human CD8(+)/TCR alpha beta(+) T cells that have a regulatory phenotype and function. We expanded and cloned these cells using autologous LPS-activated dendritic cells. The clones were not cytolytic, but responded in an autoreactive HLA class I-restricted fashion, by proliferation and production of IL-4, IL-5, IL-13 and TGF beta 1, but not IFN-gamma. They constitutively expressed CD69 and CD25 as well as molecules associated with CD4(+)CD25(+) regulatory T cells, including cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and Foxp3. They suppressed IFN-'gamma production and proliferation by CD4(+) T cells in vitro in a cell contact-dependent manner, which could be blocked using a CTLA-4-specific mAb. They were more readily isolated from patients with ankylosing spondylitis and may therefore be up-regulated in response to inflammation. We suggest that they are the CD8(+) counterparts of CD4(+) CD25(+) regulatory T cells. They resemble recently described CD8(+) regulatory cells in the rat that were able to abrogate graft-versus-host disease. Likewise, human HLA-restricted CD8(+) regulatory T cells that can be cloned and expanded in vitro may have therapeutic applications.

Cross-reactive T cell recognition of self-heat shock proteins (hsp) has been ascribed a regulatory role in inflammatory arthritis in both animal models and human disease. The previous work implies that a repertoire for epitopes in self-hsp60 should exist in normal subjects. Accordingly, we sought to generate self-hsp60-reactive T cell clones from a healthy individual using a highly purified preparation of recombinant human (Hu) hsp60. Epitope mapping using synthetic peptides and truncated constructs indicated that the T cell clones obtained actually recognized hsp60 derived from Escherichia coli. Using a series of alanine-substituted peptides and additional appropriate synthetic peptides, it was demonstrated that the clones maintain self-tolerance because of their sensitivity to an asparagine to aspartic acid sequence difference between E. coli and HuHsp60 in the epitope-containing peptide. In addition, despite substantial conservation of sequence, the homologous peptide from HuHsp60 did not compete with the E. coli-derived peptide for recognition or antagonize responses by acting as an altered peptide ligand. The results suggest that, even when the immune system targets a highly conserved epitope in bacterial hsp60, self-tolerance is maintained. Furthermore, the finding that T cell clones specific for minor contaminant proteins in HuHsp60 preparations can readily be isolated raises the possibility that the HuHsp60 facilitates presentation of antigenic proteins to the immune system.