MHCII-independent CD4+ T cells protect injured CNS neurons via IL-4

J Clin Invest. 2015 Feb;125(2):699-714. doi: 10.1172/JCI76210. Epub 2015 Jan 20.

Abstract

A body of experimental evidence suggests that T cells mediate neuroprotection following CNS injury; however, the antigen specificity of these T cells and how they mediate neuroprotection are unknown. Here, we have provided evidence that T cell-mediated neuroprotection after CNS injury can occur independently of major histocompatibility class II (MHCII) signaling to T cell receptors (TCRs). Using two murine models of CNS injury, we determined that damage-associated molecular mediators that originate from injured CNS tissue induce a population of neuroprotective, IL-4-producing T cells in an antigen-independent fashion. Compared with wild-type mice, IL-4-deficient animals had decreased functional recovery following CNS injury; however, transfer of CD4+ T cells from wild-type mice, but not from IL-4-deficient mice, enhanced neuronal survival. Using a culture-based system, we determined that T cell-derived IL-4 protects and induces recovery of injured neurons by activation of neuronal IL-4 receptors, which potentiated neurotrophin signaling via the AKT and MAPK pathways. Together, these findings demonstrate that damage-associated molecules from the injured CNS induce a neuroprotective T cell response that is independent of MHCII/TCR interactions and is MyD88 dependent. Moreover, our results indicate that IL-4 mediates neuroprotection and recovery of the injured CNS and suggest that strategies to enhance IL-4-producing CD4+ T cells have potential to attenuate axonal damage in the course of CNS injury in trauma, inflammation, or neurodegeneration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / immunology*
  • Axons / pathology
  • Brain Injuries / genetics
  • Brain Injuries / immunology*
  • Brain Injuries / pathology
  • CD4-Positive T-Lymphocytes / immunology*
  • CD4-Positive T-Lymphocytes / pathology
  • Extracellular Signal-Regulated MAP Kinases / genetics
  • Extracellular Signal-Regulated MAP Kinases / immunology
  • Histocompatibility Antigens Class II / genetics
  • Histocompatibility Antigens Class II / immunology*
  • Interleukin-4 / genetics
  • Interleukin-4 / immunology*
  • MAP Kinase Signaling System / genetics
  • MAP Kinase Signaling System / immunology*
  • Mice
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / immunology
  • Neurodegenerative Diseases / genetics
  • Neurodegenerative Diseases / immunology*
  • Neurodegenerative Diseases / pathology
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / immunology
  • Receptors, Antigen, T-Cell / genetics
  • Receptors, Antigen, T-Cell / immunology

Substances

  • Histocompatibility Antigens Class II
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Receptors, Antigen, T-Cell
  • Interleukin-4
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases