title: Disruption of the interaction of T cells with antigen-presenting cells by the active leflunomide metabolite teriflunomide: involvement of impaired integrin activation and immunologic synapse formation.
abstract: OBJECTIVE
  Leflunomide, a potent disease-modifying antirheumatic drug of the isoxazole class, exhibits antiinflammatory, antiproliferative, and immunosuppressive effects by largely unknown mechanisms, although alterations of pyrimidine synthesis have been proposed. Successful immune responsiveness requires T cell activation by interaction with antigen-presenting cells (APCs), and integrin activation and formation of an immunologic synapse (IS). In this study, we evaluated the impact of the active leflunomide metabolite teriflunomide on T cell integrin activation, evolution of the IS, and antigen-specific formation of stable T cell/APC conjugates.
  
  
  METHODS
  Effects of pharmacologic concentrations of teriflunomide on CD3/CD28- and lymphocyte function-associated antigen 1-induced signal transduction and activation of primary human T cells were investigated. Furthermore, T cells were stimulated with superantigen- and antigen-pulsed APCs to study relocalization of molecules to the IS and T cell/APC conjugate formation.
  
  
  RESULTS
  Teriflunomide inhibited T cell receptor (TCR)/CD3-mediated calcium mobilization, but other critical T cell signaling events, including activation of MAPK and NF-kappaB, remained unaltered. In contrast, inhibition of TCR/CD3-triggered beta1,2 integrin avidity and integrin-mediated costimulation (outside-in signaling) by teriflunomide revealed a striking interference with integrin function that was independent of altered pyrimidine synthesis. Moreover, teriflunomide abolished molecule relocalization to the IS and induction of T cell/APC conjugates.
  
  
  CONCLUSIONS
  These data show that the active metabolite of leflunomide prevents the interaction of T cells with APCs to form an IS. Since IS formation is crucial for eliciting an immune response, this novel mechanism could underlie the beneficial effects of leflunomide in immune-mediated disorders such as rheumatoid arthritis.
authors.affiliation: Medical University of Vienna, Vienna, Austria.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Zeyda
authors.forename: Marko
authors.initials: M
authors.lastname: Poglitsch
authors.forename: René
authors.initials: R
authors.lastname: Geyeregger
authors.forename: Josef S
authors.initials: JS
authors.lastname: Smolen
authors.forename: Gerhard J
authors.initials: GJ
authors.lastname: Zlabinger
authors.forename: Walter H
authors.initials: WH
authors.lastname: Hörl
authors.forename: Werner
authors.initials: W
authors.lastname: Waldhäusl
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Stulnig
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Säemann
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism; D000938:Antigen-Presenting Cells / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects; D003437:Crotonates; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006885:Hydroxybutyrates / Q000494:pharmacology*; D007165:Immunosuppression Therapy; D016023:Integrins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007555:Isoxazoles / Q000378:metabolism; D019169:Jurkat Cells / Q000187:drug effects; D000077339:Leflunomide; D009570:Nitriles; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D018089:Superantigens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D014052:Toluidines
chemical_list: D000814:Aniline Compounds; D000894:Anti-Inflammatory Agents, Non-Steroidal; D003437:Crotonates; D006885:Hydroxybutyrates; D016023:Integrins; D007555:Isoxazoles; D009570:Nitriles; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D018089:Superantigens; D014052:Toluidines; D018799:Intercellular Adhesion Molecule-1; C527525:teriflunomide; D000077339:Leflunomide