T-cell antigen receptor function: the concept of autoaggression

That T lymphocytes must recognize major histocompatibility complex (MHC)-encoded self antigen together with foreign antigen for effective interaction with antigen-bearing cells has been known for a decade, yet the exact function of the MHC in regulating the action of T lymphocytes is still a matter of dispute. Theories advanced to explain T-cell function assign merely an accessory role to the MHC, namely to 'restrict' the ability of T cells to respond to foreign antigen. Here Michael Hoffmann discusses the possibility that, instead of restricting T-cell activity, recognition of MHC-encoded self-antigen by the T-cell receptor is actually the consequential event in T-cell ffector function and that foreign antigen plays an accessory role.