title: CD2 and CD3 receptor-mediated tolerance: constraints on T cell activation.
abstract: BACKGROUND
  Antigen specific allograft tolerance is induced in mice by anti-CD2 plus anti-CD3epsilon monoclonal antibody (mAb) treatment. Because anti-CD2 mAb inhibits several aspects of anti-CD3epsilon driven T cell activation, we investigated what components of T cell activation are required or may be dispensed with for tolerance induction. Anti-CD3epsilon-mediated T cell activation depends on FcgammaR interactions.
  
  
  METHODS
  To assess the role of FcgammaR-mediated T cell activation in tolerance induction, FcgammaR binding IgG or non-binding IgG3 anti-CD3epsilon mAbs were examined.
  
  
  RESULTS
  These mAbs, administered in conjunction with anti-CD2, were equally effective in inducing tolerance. Moreover, in vivo administration of a blocking mAb directed against the FcgammaR, or the use of allograft recipients deficient in FcgammaR, had no effect on tolerance induction. Blocking IL-2 using mAb directed against IL-2 or IL-2R also did not prevent the induction of tolerance. These results suggest that complete T cell activation was not required for tolerance induction. However, substitution of a partially activating mAb, directed against the T cell receptor (TCR) beta subunit for anti-CD3epsilon, failed to synergize with anti-CD2 mAb to induce tolerance. The anti-TCRbeta mAb and anti-CD3epsilon mAb were found to differentially down modulate expression of TCR/CD3 complex subunits. In particular, anti-CD3epsilon caused transient down modulation of the TCRbeta receptor subunit and the TCRzeta signaling module, and this pattern was enhanced and prolonged by anti-CD2. Anti-TCRbeta caused persistent TCRzeta modulation but no TCRbeta modulation, and anti-CD2 did not influence this pattern.
  
  
  CONCLUSIONS
  These results suggest that, although full T cell activation is not required for the induction of tolerance by anti-CD2 plus anti-CD3epsilon mAb, a signal transduction pathway that is associated with TCRbeta and TCRzeta expression, and, specifically, is perturbed by mAb binding of the CD3epsilon epitope, is critical.
authors: Department of Surgery, University of Michigan, Ann Arbor 48104, USA.
authors: J D
authors: JD
authors: Punch
authors: J
authors: J
authors: Lin
authors: J
authors: J
authors: Bluestone
authors: J S
authors: JS
authors: Bromberg
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D018801:CD2 Antigens / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D005260:Female; D007108:Immune Tolerance; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D017452:Receptors, IgG / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018801:CD2 Antigens; D017252:CD3 Complex; D016693:Receptors, Antigen, T-Cell, alpha-beta; D017452:Receptors, IgG