Differential contribution of Fas- and perforin-mediated mechanisms to the cell-mediated cytotoxic activity of naive and in vivo-primed intestinal intraepithelial lymphocytes.
Intestinal intraepithelial lymphocytes (IELs) are known to exert strong constitutive cytotoxic activity. In the present study we compared the Ag-specific cytotoxic activity and the effector mechanisms involved in non-Ag-primed, naive and in in vivo-primed IELs and splenic CD8 T cells. Ex vivo isolated naive CD8alphaalpha TCRalphabeta IELs, CD8alphabeta IELs, and splenocytes from lymphocytic choriomeningitis virus (LCMV)-specific TCR transgenic mice exert Ag-specific cytotoxic activity in a long-term, but not in a short-term, cytotoxicity assay. This cytotoxic activity is mainly Fas-Fas ligand mediated and is significantly reduced in the presence of 20 microg/ml Fas-Fcgamma1 fusion protein. Both CD8alphabeta IELs and CD8alphabeta splenocytes isolated from LCMV-infected C57BL/6 mice exert potent perforin-dependent cell-mediated cytotoxicity. CD8alphaalpha TCRalphabeta IELs from LCMV-infected animals, however, show only minimal Ag-specific cytotoxicity. The potent cytotoxic activity of in vivo activated CD8alphabeta IELs is not affected by the addition of Fas-Fcgamma1. Nevertheless CD8alphabeta IELs from LCMV-infected perforin-deficient mice exert Ag-specific cytotoxicity in a short-term cytotoxicity assay, and this cytotoxicity is almost completely blocked by the addition of Fas-Fcgamma1. These results demonstrate that naive CD8alphabeta IELs exert Ag-specific, Fas-Fas ligand-mediated, constitutive cytotoxic activity in a long-term cytotoxicity assay, whereas primed CD8alphabeta IELs primarily use the perforin-dependent exocytosis pathway to exert their potent cytotoxic activity. Furthermore, these results clearly illustrate the requirement for Ag-specific determination of IEL-mediated cytotoxicity, because the elevated, but variable, frequencies of memory-type T cells in this compartment may lead to ambiguous results when polyclonal activation or redirected assays are used.
Corazza
N
N
Institute of Pathology, Division of Immunopathology, University of Bern, Switzerland.
Müller
S
S
Brunner
T
T
Kägi
D
D
Mueller
C
C
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002469:Cell Separation; D003602:Cytotoxicity, Immunologic; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D053222:Fas Ligand Protein; D007111:Immunity, Cellular; D007399:Interphase / Q000276:immunology; D007413:Intestinal Mucosa / Q000166:cytology* / Q000276:immunology* / Q000821:virology; D008024:Ligands; D008216:Lymphocytic Choriomeningitis / Q000276:immunology; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000821:virology; D019014:fas Receptor / Q000502:physiology*
D018984:Epitopes, T-Lymphocyte; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor; D054353:Perforin