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Real Time Detection of In Vitro Tumor Cell Apoptosis Induced by CD8+ T Cells to Study Immune Suppressive Functions of Tumor-infiltrating Myeloid Cells
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Superantigen reactive Vbeta6+ T cells induce perforin/granzyme B mediated caspase-independent apoptosis in tumour

S Müerköster1, M A Weigand, C Choi

  • 1Division of Cellular Immunology, G0100, Tumorimmunology Program, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.

British Journal of Cancer
|March 5, 2002
PubMed

Insights

Viral superantigen 7 triggers rapid T cell-mediated killing of lymphoma cells via perforin and granzyme B, bypassing caspases and mitochondria. This mechanism, combined with nitric oxide, may explain effective graft-vs-leukemia responses.

Area of Science:

  • Immunology
  • Cell Biology
  • Oncology

Background:

  • Endogenous viral superantigen 7 (VSA7) is a target antigen on ESb-MP lymphoma cells in DBA/2 mice.
  • Allogeneic Vbeta6+ T cells recognize VSA7 and mediate graft-vs-leukemia (GvL) reactivity.
  • Understanding the precise killing mechanism is crucial for GvL therapy optimization.

Purpose of the Study:

  • To elucidate the mechanism of superantigen-specific tumor cell lysis mediated by Vbeta6+ T cells.
  • To differentiate this rapid lysis from other known apoptotic pathways.
  • To explore potential synergistic interactions in a GvL model.

Main Methods:

  • Co-incubation of Vbeta6+ T cells with VSA7+ ESb-MP tumor cells.
  • Assessment of apoptosis using Annexin V staining and DNA fragmentation assays.
  • Analysis of cell death pathways, including death-inducing ligands, perforin/granzyme B, nitric oxide, mitochondria, and caspases.

Main Results:

  • VSA7+ ESb-MP cells exhibited rapid apoptosis (Annexin V-positivity, DNA fragmentation) within 10 minutes of co-incubation with Vbeta6+ T cells.
  • This rapid cell death was mediated by perforin and granzyme B, independent of CD95L, TRAIL, TNF, mitochondria, or caspases.
  • Nitric oxide induced a slower, caspase- and mitochondria-dependent apoptosis in the same tumor cells.
  • A synergistic effect between T cell-mediated lysis and nitric oxide was observed.

Conclusions:

  • Viral superantigen 7-specific cytotoxic T lymphocytes induce rapid tumor cell apoptosis via a non-canonical perforin/granzyme B pathway.
  • This rapid lysis mechanism bypasses conventional mitochondrial and caspase-dependent apoptosis.
  • Synergy between cytotoxic T lymphocytes and nitric oxide may contribute to effective immune rejection in GvL models, including metastatic cancer.

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