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Published on: June 29, 2011

Critical role for mitochondria in B cell receptor-mediated apoptosis

A Bouchon1, P H Krammer, H Walczak

  • 1Tumor Immunology Program, German Cancer Research Center (DKFZ), Heidelberg, Germany. bouchon@bii.ch

European Journal of Immunology
|December 22, 1999
PubMed

Insights

B cell receptor (BCR)-mediated apoptosis, crucial for immune tolerance, is initiated by mitochondrial permeability transition, not caspase-8. This process releases cytochrome c, activating downstream caspases for cell death.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • B cell apoptosis is vital for immune tolerance, eliminating self-reactive B cells.
  • The precise mechanisms of B cell receptor (BCR)-mediated apoptosis remain largely unelucidated.
  • Understanding BCR signaling is key to immune repertoire regulation.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying BCR-mediated apoptosis in human germinal center B cells.
  • To determine the role of caspases and mitochondrial pathways in BCR-induced B cell death.
  • To differentiate BCR-mediated apoptosis from T cell activation-induced cell death.

Main Methods:

  • Utilized the human Burkitt lymphoma cell line BL60 as a model for germinal center B cells.
  • Examined the requirement for transcriptional activity in BCR-mediated apoptosis.
  • Assessed the involvement of death receptors and caspase-8 activation.
  • Monitored cytochrome c release and mitochondrial permeability transition (PT).
  • Investigated the effects of caspase inhibition on BCR-induced apoptosis.

Main Results:

  • BCR-mediated apoptosis requires transcriptional activity.
  • It does not involve known death receptor systems or initial caspase-8 activation.
  • Cytochrome c release and mitochondrial PT precede caspase activation during BCR signaling.
  • Caspase inhibition blocks downstream events but not mitochondrial PT, cytochrome c release, or cell death.

Conclusions:

  • BCR-mediated apoptosis is initiated by caspase-independent mitochondrial PT.
  • This leads to cytochrome c release, activating caspase-9 and subsequent apoptotic pathways.
  • The findings reveal a distinct apoptotic pathway initiated by BCR signaling.

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