title: MHC-restricted and -unrestricted CD8 T cells: an evolutionary perspective.
abstract: BACKGROUND
  In mammals, cytotoxic CD8 T cells are crucial effectors of a typical adaptive cellular immune response. They recognize and kill cells that express at their surface antigenic peptides complexed to major histocompatibility complex (MHC) class I molecules. Although T cells (undefined as to CD determinants) and associated in vitro cytotoxic activity have been described in a few amphibian and teleost species, their in vivo functions have yet to be characterized.
  
  
  RESULTS
  CD8 function has been investigated in the frog Xenopus by antibody depletion, skin allografting, and tumor transplantation. Injection of adult frogs with anti-Xenopus CD8 monoclonal antibody effects transient CD8 T-cell depletion in vivo that correlates with delayed rejection of MHC-disparate skin allografts and an impaired immune response against transplanted syngeneic MHC class I-negative tumors.
  
  
  CONCLUSIONS
  For the first time, CD8 T cells have been shown to be involved in acute skin allograft rejection in an ectothermic vertebrate. Our data also suggest that, at least in Xenopus, T cells that express a CD8 epitope may be effectors in MHC-unrestricted anti-tumor responses.
authors.affiliation: Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors.forename: L
authors.initials: L
authors.lastname: Rau
authors.forename: N
authors.initials: N
authors.lastname: Cohen
authors.forename: J
authors.initials: J
authors.lastname: Robert
mesh_terms: D000818:Animals; D005075:Biological Evolution; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D017637:Clonal Deletion; D006084:Graft Rejection; D006649:Histocompatibility Antigens / Q000276:immunology*; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000276:immunology; D016038:Skin Transplantation / Q000276:immunology; D014981:Xenopus
chemical_list: D006649:Histocompatibility Antigens