Receptor cross-talk spatially restricts p-ERK during TLR4 stimulation of autoreactive B cells

J Immunol. 2012 Oct 15;189(8):3859-68. doi: 10.4049/jimmunol.1200940. Epub 2012 Sep 14.

Abstract

To maintain tolerance, autoreactive B cells must regulate signal transduction from the BCR and TLRs. We recently identified that dendritic cells and macrophages regulate autoreactive cells during TLR4 activation by releasing IL-6 and soluble CD40 ligand (sCD40L). These cytokines selectively repress Ab secretion from autoreactive, but not antigenically naive, B cells. How IL-6 and sCD40L repress autoantibody production is unknown. In this work, we show that IL-6 and sCD40L are required for low-affinity/avidity autoreactive B cells to maintain tolerance through a mechanism involving receptor cross-talk between the BCR, TLR4, and the IL-6R or CD40. We show that acute signaling through IL-6R or CD40 integrates with chronic BCR-mediated ERK activation to restrict p-ERK from the nucleus and represses TLR4-induced Blimp-1 and XBP-1 expression. Tolerance is disrupted in 2-12H/MRL/lpr mice where IL-6 and sCD40L fail to spatially restrict p-ERK and fail to repress TLR4-induced Ig secretion. In the case of CD40, acute signaling in B cells from 2-12H/MRL/lpr mice is intact, but the chronic activation of p-ERK emanating from the BCR is attenuated. Re-establishing chronically active ERK through retroviral expression of constitutively active MEK1 restores tolerance upon sCD40L, but not IL-6, stimulation, indicating that regulation by IL-6 requires another signaling effector. These data define the molecular basis for the regulation of low-affinity autoreactive B cells during TLR4 stimulation; they explain how autoreactive but not naive B cells are repressed by IL-6 and sCD40L; and they identify B cell defects in lupus-prone mice that lead to TLR4-induced autoantibody production.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoantibodies / biosynthesis*
  • B-Lymphocyte Subsets / immunology*
  • B-Lymphocyte Subsets / metabolism*
  • B-Lymphocyte Subsets / pathology
  • CD40 Antigens / metabolism
  • CD40 Ligand / metabolism
  • Cell Nucleus / enzymology
  • Cell Nucleus / metabolism
  • Cells, Cultured
  • Coculture Techniques
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Female
  • Immune Tolerance / genetics
  • Lupus Nephritis / enzymology
  • Lupus Nephritis / immunology
  • Lupus Nephritis / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred MRL lpr
  • Mice, Transgenic
  • Nuclear Proteins / antagonists & inhibitors
  • Nuclear Proteins / metabolism
  • Protein Transport / genetics
  • Protein Transport / immunology
  • Receptor Cross-Talk / immunology*
  • Receptors, Antigen, B-Cell / physiology
  • Receptors, Interleukin-6 / metabolism
  • Signal Transduction / genetics
  • Signal Transduction / immunology
  • Toll-Like Receptor 4 / physiology*

Substances

  • Autoantibodies
  • CD40 Antigens
  • Nuclear Proteins
  • Receptors, Antigen, B-Cell
  • Receptors, Interleukin-6
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • CD40 Ligand
  • Extracellular Signal-Regulated MAP Kinases