Lack of activation induced cell death in human T blasts despite CD95L up-regulation: protection from apoptosis by MEK signalling

Immunology. 1999 Dec;98(4):569-75. doi: 10.1046/j.1365-2567.1999.00925.x.

Abstract

The generation of effective immunity requires that antigen-specific T cells are activated, clonally expanded and ultimately eliminated by apoptosis. The involvement of CD95-mediated apoptosis in T-cell elimination is well established, but the conditions which regulate the death pathway under normal circumstances are still emerging. Using superantigen-activated human T cells, we found that whilst T-cell receptor (TCR) signalling triggered up-regulation of CD95 ligand (CD95L), the majority of T cells were resistant to apoptosis induction, despite co-expressing high levels of CD95. Resistance was maintained following direct antibody-mediated cross-linking of CD95 and was not confined to early time periods following activation. Our data implicate TCR-derived signals in protection from apoptosis and reveal a role for the mitogen-activated protein (MAP) kinase pathway by use of a MAP kinase kinase (MEK) inhibitor. Collectively these data demonstrate that resistance to activation-induced cell death in human T cells is prolonged rather than transient, is not attributable to a lack of CD95L up-regulation and is due, at least in part, to signalling via the MEK pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal / pharmacology
  • Apoptosis*
  • Biological Assay
  • CD3 Complex / metabolism
  • Calcium / metabolism
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Fas Ligand Protein
  • Flavonoids / pharmacology
  • Flow Cytometry
  • Humans
  • In Situ Nick-End Labeling
  • Lymphocyte Activation*
  • MAP Kinase Signaling System / drug effects*
  • Membrane Glycoproteins / analysis
  • Membrane Glycoproteins / metabolism*
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
  • Receptors, Antigen, T-Cell / metabolism
  • T-Lymphocytes / metabolism*
  • Tetradecanoylphorbol Acetate / pharmacology
  • fas Receptor / immunology
  • fas Receptor / metabolism

Substances

  • Antibodies, Monoclonal
  • CD3 Complex
  • Enzyme Inhibitors
  • FASLG protein, human
  • Fas Ligand Protein
  • Flavonoids
  • Membrane Glycoproteins
  • Receptors, Antigen, T-Cell
  • fas Receptor
  • Mitogen-Activated Protein Kinase Kinases
  • Tetradecanoylphorbol Acetate
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
  • Calcium