title: Leukocyte function-associated antigen-1-dependent lysis of Fas+ (CD95+/Apo-1+) innocent bystanders by antigen-specific CD8+ CTL.
abstract: Exquisite specificity toward Ag-bearing cells (cognate targets) is one of the most important properties of CD8+ CTL-mediated cytotoxicity. Using highly Ag-specific CD8+ CTL lines and clones, which spare noncognate, Ag-free targets, we found that in the presence of Ag-bearing targets the CTL acquire the ability to lyse noncognate target cells (bystanders). It is shown that the unexpectedly rapid and efficient lysis of bystanders by Ag-activated CTL is mediated by a Fas ligand (FasL)/Fas-based mechanism and does not depend on perforin. The CTL lysed Fas-expressing bystanders, but spared the Fas-negative or anti-Fas mAb-resistant bystander cells. Accordingly, the FasL-deficient gld/gld CTL did not kill bystanders, while perforin-deficient CTL did. Unlike anti-Fas mAb-induced cell death, the lysis of bystanders was not only FasL/Fas dependent but also required adhesion molecule LFA-1 on the surface of the activated CTL. Lysis of bystanders is viewed as acceptable "collateral" damage, but the persistent presence of activated CTL could result in immunopathologies involving functional Fas-expressing tissues.
authors.affiliation: Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kojima
authors.forename: K
authors.initials: K
authors.lastname: Eshima
authors.forename: H
authors.initials: H
authors.lastname: Takayama
authors.forename: M V
authors.initials: MV
authors.lastname: Sitkovsky
mesh_terms: D000818:Animals; D016827:CD8 Antigens; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016923:Cell Death / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D016169:Lymphocyte Function-Associated Antigen-1 / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor / Q000276:immunology*
chemical_list: D016827:CD8 Antigens; D016169:Lymphocyte Function-Associated Antigen-1; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor; D054353:Perforin