TLR9-mediated signals rescue B-cells from Fas-induced apoptosis via inactivation of caspases

Immunol Lett. 2012 Mar 30;143(1):77-84. doi: 10.1016/j.imlet.2012.02.006.

Abstract

The death receptor, CD95/Fas, serves to eliminate potentially dangerous, self-reactive B cells. Engagement of B-cell receptors (BCR) on mature B-cells mediates the escape from cell death resulting in the activation and expansion of antigen specific clones. In addition to the antigen receptors, the receptors of B-cell activating factor belong to the tumor necrosis factor (TNF) family (BAFFR); moreover, the pattern recognition receptor, TLR9 may also deliver survival signals inhibiting Fas-mediated death of B-cells. Our aim was to compare the mechanism of BCR-induced and the BAFFR- or TLR9-stimulated rescue of B-cells from CD95/Fas-mediated apoptosis. We have found that BAFFR and TLR9 collaborate with BCR to protect B-cells from Fas-induced elimination and the rescue is independent of protein synthesis. The results revealed that the TLR9- and BCR-triggered rescue signals are transmitted through partially overlapping pathways; the protein kinase C (PKC) and the abl kinase induced phosphorylation may inactivate caspases in both CpG and anti-IgG stimulated cells. However, PI3-K activation is crucial upon the BCR driven anti-apoptotic effect, while p38 MAPK-mediated inactivation of caspases seems to play essential role in TLR9-mediated protection against Fas-induced programmed cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis*
  • B-Cell Activation Factor Receptor / immunology
  • B-Lymphocytes / cytology
  • B-Lymphocytes / immunology*
  • B-Lymphocytes / metabolism
  • Caspases / metabolism*
  • Cell Line, Tumor
  • Enzyme Activation
  • Mice
  • Receptors, Antigen, B-Cell / immunology
  • Signal Transduction*
  • Toll-Like Receptor 9 / immunology*
  • Toll-Like Receptor 9 / metabolism
  • fas Receptor / immunology*

Substances

  • B-Cell Activation Factor Receptor
  • Receptors, Antigen, B-Cell
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9
  • fas Receptor
  • Caspases