title: Suppression of the cell-mediated immune response by a Fas-immunoglobulin fusion protein.
abstract: BACKGROUND
  Immunosuppressive agents must not only be effective in impairing the host's allo-immune response, but should also be selective in targeting only those elements of the immune system activated by the allograft. The fact that allo-activated T cells express surface protein molecules that are not typically present on resting T cells can be exploited to specifically target this population. Fas ligand is one such molecule whose cell surface expression on T cells is dramatically up-regulated upon activation.
  
  
  METHODS
  We constructed a murine fusion protein by linking the extracellular domain of Fas to the Fc region of IgG2a. The rationale being to selectively target activated T cells via binding of its Fas moiety to cell surface Fas ligand, and then to allow the Fc moiety to invoke its usual effector mechanisms resulting in the destruction of the allo-activated T cell. Here, we describe the design and expression of Fas-IgG2a and characterize several key in vitro and in vivo properties of this fusion protein including its ability to impact on both cell-mediated immune responses and cellular apoptotic activity using a murine model of delayed-type hypersensitivity.
  
  
  RESULTS
  In vitro, our Fas-IgG2a construct bound activated T cells via FasL and invoked cytotoxicity. In vivo, it demonstrated a prolonged half-life characteristic of an immunoglobulin-like molecule. Most significantly, it suppressed the cell-mediated immune response and diminished cellular apoptotic activity in lymphoid tissue in our murine model.
  
  
  CONCLUSIONS
  Fas-IgG2a is a novel agent for delivering target-specific immunosuppression with potential applicability in the transplant setting.
authors.affiliation: Yingnian Shen, Genomics and Proteomics Science, GlaxoSmithKline, Research Triangle Park, North Carolina, USA.
authors.forename: Yingnian
authors.initials: Y
authors.lastname: Shen
authors.forename: Barbara
authors.initials: B
authors.lastname: Young
authors.forename: Mark L
authors.initials: ML
authors.lastname: Lipman
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053222:Fas Ligand Protein; D006968:Hypersensitivity, Delayed / Q000276:immunology / Q000517:prevention & control; D007111:Immunity, Cellular / Q000187:drug effects; D007074:Immunoglobulin G / Q000235:genetics / Q000494:pharmacology*; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000494:pharmacology; D048069:Tumor Necrosis Factors / Q000235:genetics / Q000494:pharmacology*
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D048069:Tumor Necrosis Factors