Activation-driven T cell death. II. Quantitative differences alone distinguish stimuli triggering nontransformed T cell proliferation or death.
Clonal deletion is the major mechanism by which T cell tolerance is achieved in vivo. The process of activation-driven cell death, originally characterized with T cell hybridomas, likely represents the mechanism of clonal deletion because it shares a number of properties with the in vivo process, especially the ability to be triggered in an Ag-specific manner, the cell-autonomous nature of the response, and its sensitivity to the drug cyclosporin A. We now have extended our analysis of activation-driven cell death to clonal populations of nontransformed T cells. Activation-driven cell death can be induced in nontransformed T lymphocytes by combinations of mitogenic stimuli. In particular, two mitogenic stimuli at high dose, one a lymphokine and the other delivered via the TCR or another activation structure, are required to induce activation-driven cell death. Activation-driven cell death is an active cell suicide process with attributes typical of physiological cell death, including early nuclear disintegration and a requirement for macromolecular synthesis, and is distinct from death by factor deprivation. Susceptibility to the induction of cell death by antigenic or activating stimulation is a common aspect of most T cells and is consistent with observations that clonal deletion can occur throughout T cell ontogeny. Most importantly, the alternative cellular responses of cell death and cell proliferation in nontransformed T cells appear to be triggered solely as a function of quantitative differences in the doses of identical stimuli. This can be viewed as a dose-dependent switch that determines cell fate. Developmental regulation of this switch may explain the processes of positive and negative selection during T cell ontogeny and also provide a mechanistic rationale for a strategy of selective anti-tumor therapy.
Ucker
D S
DS
Division of Immunology, Medical Biology Institute, La Jolla, CA 92037.
Meyers
J
J
Obermiller
P S
PS
D000818:Animals; D000941:Antigens / Q000276:immunology; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008815:Mice, Inbred Strains; D012313:RNA / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000502:physiology*
D000941:Antigens; D007376:Interleukin-2; D012313:RNA; D016572:Cyclosporine