title: Cytotoxic pathways in the skin allograft rejection by CD4+ T cells.
abstract: BACKGROUND
  Two major mechanisms of T cell-mediated cytotoxicity are known: perforin-dependent and Fas-dependent cytotoxic pathways. Previous studies in vitro demonstrated that CD4+ cytotoxic T lymphocytes use the Fas pathway as a primary cytotoxic mechanism, but the cytotoxic mechanisms used by CD4+ T cells in vivo are unclear.
  
  
  METHODS
  We examined the cytotoxic pathways of CD4+ T cells in vivo using a skin allograft model, in which athymic nu/nu mice were transplanted with skin allografts and reconstituted with purified CD4+T cells. Fas-deficient and perforin-deficient mice and anti-tumor necrosis factor (TNF)-alpha monoclonal antibody were used for inactivating each cytotoxic pathway in vivo.
  
  
  RESULTS
  The skin allografts from Fas-deficient mice were readily rejected by the athymic mice reconstituted with purified CD4+ T cells. Perforin-deficient CD4+ T cells could also reject Fas-deficient skin allografts. Furthermore, in vivo treatment with anti-TNF-alpha monoclonal antibody did not prevent the allograft rejection by CD4+ T cells in the absence of both Fas and perforin pathways.
  
  
  CONCLUSIONS
  These results indicate participation of undefined mechanisms other than Fas, perforin, and TNF-alpha pathways in CD4+ T cell-mediated cytotoxicity in vivo.
authors.affiliation: Department of Dermatology, Niigata University School of Medicine, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ito
authors.forename: M
authors.initials: M
authors.lastname: Minagawa
authors.forename: K
authors.initials: K
authors.lastname: Tomiyama
authors.forename: M
authors.initials: M
authors.lastname: Ito
authors.forename: K
authors.initials: K
authors.lastname: Kawai
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D006084:Graft Rejection / Q000473:pathology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D016038:Skin Transplantation / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000494:pharmacology
chemical_list: D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D054353:Perforin