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Abstract: TH-OR058

Non-Classical Monocytes Act as Glomerular Sentinels, Sensing Deposited Immune Complexes and Orchestrating the Inflammatory Response via LFA-1 in Experimental Crescentic Glomerulonephritis

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Woollard, Kevin, Imperial College London, London, United Kingdom
  • Turner-Stokes, Tabitha, Imperial College London, London, United Kingdom
  • Garcia Diaz, Ana Isabel, Imperial College London, London, United Kingdom
  • Cook, H. Terence, Imperial College London, London, United Kingdom
  • Pusey, Charles D., Imperial College London, London, United Kingdom
Background

Non-classical monocytes (NC Mo) crawl along the resting endothelium, orchestrate the inflammatory response in some vascular beds and express high levels of FcγRIII(CD16). They may be important in triggering inflammation to immune complex (IC) deposition in glomerulonephritis (GN). Nephrotoxic Nephritis (NTN) in the WKY rat is a widely used, clinically-relevant model of crescentic GN but the distinct roles of myeloid subsets and the dynamics of their glomerular recruitment are unknown.

Methods

We developed a novel rat transgenic WKY-hCD68-GFP Mo/macrophage reporter. Mo subsets and endothelial cells were sorted from glomeruli of rats with NTN to investigate effector functions. Intravital confocal microscopy, with in vivo antibody labelling, was performed in the hydronephrotic kidney of anaesthetised WKY-hCD68-GFP rats, permitting high-resolution glomerular imaging and real-time, in vivo visualisation of myeloid recruitment and intravascular behaviour during NTN.

Results

Classical and NC Mo subsets were phenotyped as GFPposCD43loHIS48hi and GFPposCD43hiHIS48int respectively and neutrophils (PMNs) as GFPnegCD43intHIS48hi. RNA expression confirmed NC Mo were CD16hiCX3CR1hiCD14loCCR2lo relative to classical Mo i.e. homologous to mice and humans.

During intravital imaging, NC Mo surveyed the glomerular endothelium for prolonged periods in the steady state. Classical Mo and PMNs had only transient endothelial interactions. There were subset-specific differences in the behavioural response to IC deposition during NTN: Increased recruitment of NC Mo vs. increased retention of classical Mo and PMNs. CD16 and pro-inflammatory cytokines (IL-1β, TNFα) were upregulated in NC compared to classical Mo and a unique chemokine axis was overexpressed by the endothelium and NC Mo. LFA-1 blockade inhibited the distinctive migratory phenotype of NC Mo, reducing their recruitment and the retention of PMNs.

Conclusion

LFA-1-mediated endothelial surveillance by CD16hi NC Mo may be an important mechanism for IC detection in GN, orchestrating the subsequent inflammatory response through a unique chemokine axis and cytokine-mediated retention of classical Mo and PMNs. Targeting NC Mo may lead to effective treatments for GN, with fewer side effects.

Funding

  • Government Support - Non-U.S.