CD8+ T cells maintain tolerance to myelin basic protein by 'epitope theft'.

Myelin basic protein-specific CD8(+) T cells can induce central nervous system autoimmunity; however, immune tolerance prevents these autoreactive cells from causing disease. To define the mechanisms that mediate tolerance, we developed two T cell receptor-transgenic mouse lines with different affinities for the H-2K(k)-restricted myelin basic protein epitope consisting of amino acids 79-87 (MBP(79-87)). We observed both thymic deletion and peripheral tolerance in the lower-affinity T cells. The higher-affinity T cells, however, showed no evidence of tolerance induction and were able to prevent tolerance of the lower-affinity T cells by removing H-2K(k)-MBP(79-87) complexes from antigen-presenting cells without proliferating. This form of immune regulation could limit responses of self-reactive T cells that escape other tolerance mechanisms.