title: Cloned cytolytic T cells can suppress primary cytotoxic responses directed against them.
abstract: In vivo and in vitro, murine peripheral T cells can suppress or "veto" the activation of cytotoxic T lymphocytes directed against antigens presented by those T cells. This suppression is antigen-specific and H-2-restricted. The recognition event initiating this suppression appears to be unidirectional; precursors of cytotoxic T lymphocytes recognize the antigen-bearing veto cell and are thereby inactivated--the veto cell need not recognize the CTL precursor. We show here that 3/3 cytolytic T cell clones can exert veto activity in vitro on normal spleen cells which do not bear antigens the T cell clones can recognize. This suppression results in greatly diminished cytotoxic activity generated during a primary 5-day mixed lymphocyte culture against antigens which the veto cell expresses, but not against third-party antigens present in the same culture. In this same system, a noncytolytic T cell clone will not serve as a source of veto cells. Secondary cytotoxic responses are relatively resistant to the veto cell activity of cloned cytolytic T cells. The cloned veto cells do not suppress the generation of cytotoxic activity directed against antigens they recognize (and presumably carry over via antigen-specific receptors). Cold target competition during the cytotoxic assay has been eliminated as a possible mechanism for T cell clone-induced suppression, and suppression cannot be reversed by the addition to the mixed lymphocyte cultures of supernatants from concanavalin A-activated spleen cells. It is suggested that this mechanism of inactivating primary cytotoxic T lymphocyte responses could play an important role in the maintenance of self-tolerance and in the induction and maintenance of tolerance to allografts.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002999:Clone Cells / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D007108:Immune Tolerance; D007519:Isoantigens / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008806:Mice, Inbred AKR; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D051381:Rats; D011917:Rats, Inbred Lew; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D007519:Isoantigens; D011948:Receptors, Antigen, T-Cell