MHC-restricted and -unrestricted CD8 T cells: an evolutionary perspective

Transplantation. 2001 Dec 15;72(11):1830-5. doi: 10.1097/00007890-200112150-00020.


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.

Methods and 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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biological Evolution
  • CD8-Positive T-Lymphocytes / immunology*
  • Clonal Deletion
  • Graft Rejection
  • Histocompatibility Antigens / immunology*
  • Neoplasm Transplantation
  • Neoplasms / immunology
  • Skin Transplantation / immunology
  • Xenopus


  • Histocompatibility Antigens