T cell receptor ligation triggers novel nonapoptotic cell death pathways that are Fas-independent or Fas-dependent.
Short-term culture of activated T cells with IL-2 renders them highly susceptible to apoptotic death triggered by TCR cross-linking. Activation-induced apoptosis is contingent upon caspase activation and this is mediated primarily by Fas/Fas ligand (FasL) interactions that, in turn, are optimized by p38 mitogen-activated protein kinase (MAPK)-regulated signals. Although T cells from mice bearing mutations in Fas (lpr) or FasL (gld) are more resistant to activation-induced cell death (AICD) than normal T cells, a significant proportion of CD8(+) T cells and to a lesser extent CD4(+) T cells from mutant mice die after TCR religation. Little is known about this Fas-independent death process. In this study, we demonstrate that AICD in lpr and gld CD4(+) and CD8(+) T cells occurs predominantly by a novel mechanism that is TNF-alpha-, caspase-, and p38 MAPK-independent and has morphologic features more consistent with oncosis/primary necrosis than apoptosis. A related Fas- and caspase-independent, nonapoptotic death process is revealed in wild-type (WT) CD8(+) T cell blasts following TCR ligation and treatment with caspase inhibitors, the p38 MAPK inhibitor, SB203580, or neutralizing anti-FasL mAb. In parallel studies with WT CD4(+) T cells, two minor pathways leading to nonapoptotic, caspase-independent AICD were identified, one contingent upon Fas ligation and p38 MAPK activation and the other Fas- and p38 MAPK-independent. These data indicate that TCR ligation can activate nonapoptotic death programs in WT CD8(+) and CD8(+) T blasts that normally are masked by Fas-mediated caspase activation. Selective use of potentially proinflammatory oncotic death programs by activated lpr and gld T cells may be an etiologic factor in autosensitization.
Davidson
Wendy F
WF
Department of Immunology, Holland Laboratory, American Red Cross, Rockville, MD 20855, USA. davidsonw@usa.redcross.org
Haudenschild
Christian
C
Kwon
Jaeyul
J
Williams
Mark S
MS
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000276:immunology*; D053222:Fas Ligand Protein; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018448:Models, Immunological; D017382:Reactive Oxygen Species / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D011948:Receptors, Antigen, T-Cell; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases