Bcl-2 protects against Fas-based but not perforin-based T cell-mediated cytolysis.
Fas ligand and perforin are the two key effector mechanisms in T cell-mediated cytotoxicity. These molecules mediate cytolysis of target cells by membrane damage and apoptosis. bcl-2 is known to protect cells against apoptosis induced by many stimuli including growth factor removal. However bcl-2's effect on Fas ligand and perforin-induced lysis has not been studied extensively. We investigated the effect of overexpression of bcl-2 alone, Fas alone or their combined overexpression on lysis of a commonly used target, P815, by perforin-sufficient, Fas ligand-sufficient and perforin-deficient or Fas ligand-deficient, allospecific cytotoxic T lymphocytes (CTL). Wild-type P815 are susceptible to lysis by perforin-sufficient CTL, regardless of the presence or absence (gld) of Fas ligand, but are poorly lysed by perforin-deficient CTL. Fas transfection of P815 makes target cells highly susceptible to lysis by both perforin-sufficient and -deficient CTL, indicating the presence of the Fas ligand-mediated cytotoxicity on both types of CTL. Co-transfection of P815-fas with bcl-2 abolishes their increased susceptibility to Fas-mediated lysis, even in the face of Fas overexpression on the cell membrane. The protective effect of bcl-2 against cell lysis is evident with perforin-deficient CTL as effector cells or when perforin activity is eliminated by the absence of extracellular calcium in perforin-sufficient CTL. bcl-2 overexpression by P815, however, does not protect against CTL lysis by the perforin pathway, regardless of Fas overexpression, as demonstrated by fas ligand mutated gld and wild-type perforin-sufficient CTL. Therefore bcl-2 can protect P815 target cells against Fas-mediated lysis when triggered by the Fas ligand on CTL, but not against perforin-mediated lysis.
Lee
R K
RK
Department of Microbiology and Immunology, University of Miami School of Medicine, Miami, FL 33136, USA.
Spielman
J
J
Podack
E R
ER
D000818:Animals; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D053222:Fas Ligand Protein; D008407:Mast Cells; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000494:pharmacology*; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000096:biosynthesis / Q000187:drug effects*
D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor; D054353:Perforin