The GvHD Hub uses cookies on this website. They help us give you the best online experience. By continuing to use our website without changing your cookie settings, you agree to our use of cookies in accordance with our updated Cookie Policy

The role of microglia in CNS GvHD

Mar 16, 2020

Graft -versus-host disease (GvHD) is a complication observed in patients following allogeneic hematopoietic cell transplantation (allo-HCT). Primarily believed to be restricted to the skin, gastrointestinal tract and liver, pre-clinical and clinical observations have since revealed the effect of GvHD on the central nervous system (CNS). 1

T cell CNS infiltration is a key player in CNS GvHD establishment and progression. As a growing concern in the field of allo-HCT, efforts have been made to determine the mechanisms behind T cell infiltration, neuronal apoptosis and subsequent neurological deficits. 2Microglia are a tissue macrophage population found in the CNS and stand as the main major histocompatibility complex class II (MHC-II)-expressing antigen presenting cell (APC) in the CNS. 3Although microglia are important in mediating CNS immune responses, they have also been linked to the pathogenesis of a number of neurodegenerative diseases. 4A team ledby Mathew R Nimithaand Vinnakota M Janaki, University of Freiburg, Freiburg, DE, investigated microglial activation in CNS GvHD mouse models and patient samples. 2

Study design

  • The bone marrow (BM) of experimental mice was irradiated and GvHD was induced by transplantation of BM cells and CD4 +/CD8 +T cells from a mismatched donor (allo-HCT). As a control, syngeneic stem cell transplantation (syn-HCT) was performed by transplantation of BM and T cells from a donor mouse matching the genetic background of the recipient mouse
  • CNS immune infiltration and activation were measured using:
    • Immunohistochemistry (IHC) and flow cytometric (FC) quantification of CD3 +T cells
    • IHC and FC quantification of CD11b +CD45 highcells (dendritic cells, monocytes, macrophages)
    • IHC quantification of Iba-1, a microglial activation marker
    • IHC and FC quantification of MHC II- and CD80-expressing microglia
    • Transcriptome analysis of Map3k7,which encodes for transforming growth factor beta (TGF-β)-activated kinase 1 (TAK 1)
    • IHC quantification of phosphorylated (p) microglia via the markers: TAK 1, pJNK, pNF-kB, pMAPK
  • The elevated plus maze and novel object recognition tests were implemented to evaluate neurocognitive function in mice
  • GvHD was induced in Cx3cr1 creER: Tnf fl/- mice to investigate the role of tumour necrosis factor (TNF) in CNS tissue damage
  • GvHD was induced in Cx3cr1 creER:Tak1 fl/fl to investigate the role of microglial TAK1 in CNS-GvHD
  • The effect of two TAK1 inhibitors, takinib and 5Z-7-Oxozeaenol, on CNS GvHD-presenting mice was investigated
  • Formalin fixed paraffin embedded (FFPE) patient brain samples ( Institute of Neuropathology, University Hospital Freiburg, Germany) were obtained from patients that had died following allo-HCT and were either asymptomatic or had developed GvHD


  • The abundance of CD3 +T cells was significantly increased in the meninges (p< 0.005) and cortex (p= 0.001) of mice that had undergone allo-HCT but not after syn-HCT
  • The abundance of CD11b +CD45 highcells was significantly greater (p= 0.005) in mice that had undergone allo-HCT compared to syn-HCT
  • The abundance of Iba-1 +microglia cells was increased in mice that had undergone allo-HCT compared to syn-HCT (p= 0.01)
  • Features of microglial activation (reduced filament dendrite length, reduced number of dendrite segments, branching points and dendrite terminal points) were observed in allo-HCT treated, GvHD-developing mice but not in syn-HCT treated or untreated mice
  • Significant upregulation of MHC-II (p< 0.0001) and CD80 (p< 0.0001) on CD11b +CD45 highcells was observed in allo-HCT treated mice compared to syn-HCT treated or untreated mice
  • In mice that developed GvHD, p38 MAPK phosphorylation was increased, indicating activation of the MAPK/NF-κB pathway
  • TNF knockout (KO) mice exhibited reduced number of CD3 +T cells in the CNS
  • NF-κB-mediated TAK1 activation was driven by TNF in mice
  • Microglial TAK1 KO mice exhibited reduced of CD3 +cell in the CNS, reduced microglial MHC-II expression and improved neurocognitive function while maintaining peripheral GvHD presentation
  • Pharmaceutical inhibition of TAK1 in mice resulted in reduced:
    • CNS CD3 +T cells and Iba-1 +microglia
    • CNS Th1 and Th17 cells
    • MHC-II expression by microglia
    • TNF production by microglia
    • Endothelial vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) expression on CNS endothelial cells
  • In-vivopharmaceutical inhibition of TAK1 improved neurocognitive function in mice
  • The number of Iba-1 +microglia was increased in human patients who developed acute GvHD (aGvHD) following allo-HCT compared to those who did not
  • The number of TNF and Iba-1 double positive microglia was significantly increased in patients who developed aGvHD compared to those who did not


  • Microglia play a crucial role in the establishment of CNS GvHD; augmenting T-cell stimulation and migration into the CNS
  • The microglial TAK1/TNF/MHC-II axis is imperative in the initiation and maintenance of CNS GvHD
  • The data from this study provides the grounds for investigating TAK1 inhibition in phase I clinical trials for the treatment of CNS GvHD
  1. Hartrampf S. et al. The central nervous system is a target of acute graft versus host disease in mice. Blood. 2013 March 7; 121(10): 1906–10. DOI: 10.1182/blood-2012-09-456590
  2. Mathew R.N. et al. Graft-versus-host disease of the CNS is mediated by TNF upregulation in microglia. J Clin Invest. 2019 December 17. DOI: 10.1172/JCI130272
  3. Schetters S.T.T. et al. Neuroinflammation: Microglia and T Cells Get Ready to Tango. Front. Immunol. 25 January 2018.DOI: 10.3389/fimmu.2017.01905
  4. Bachiller S. et al. Microglia in Neurological Diseases: A Road Map to Brain-Disease Dependent-Inflammatory Response. Front Cell Neurosci. 2018 December 18. DOI: 10.3389/fncel.2018.00488