Abstract: TH-PO054

Monocytes Promote Crescent Formation in Anti-Myeloperoxidase Antibody-Induced Glomerulonephritis

Session Information

Category: Glomerular

  • 1001 Glomerular: Basic/Experimental Immunology and Inflammation

Authors

  • Rousselle, Anthony, ECRC, Berlin, Germany
  • Kettritz, Ralph, Charite Berlin, Berlin, Germany
  • Schreiber, Adrian, Charite Berlin, Berlin, Germany
Background

Neutrophils and monocytes express ANCA antigens, and activation of these cells by ANCA is central to ANCA-associated vasculitis (AAV) and necrotizing crescentic glomerulonephritis (NCGN). The importance of neutrophils is established; however, any role of monocytes is less clear. We tested the hypothesis that depletion of CCR2+ inflammatory monocytes and their derivatives would abrogate anti-MPO antibody-induced NCGN in a mouse model.

Methods

We used anti-MPO IgG (50 µg/g body weight, BW) transfer to induce NCGN in LPS-challenged wild-type (WT) mice and in mice expressing the CCR2 promoter-controlled diphtheria toxin receptor (CCR2-DTR). Diphteria toxin (DT) then allows depletion of CCR2+Ly6Chigh inflammatory monocytes in DTR mice. Urine was analyzed by dipstick, albuminuria by ELISA, glomerular necrosis and crescents by histology, and circulating and renal cell influx by flow cytometry.

Results

Both mouse strains showed similar circulating Ly6Chi and -lo monocytes and neutrophils at baseline. Diphtheria toxin robustly depleted circulating monocytes only in CCR2-DTR mice, whereas neutrophil numbers were similar. Anti-MPO antibody transfer resulted in nephritic urine by dipstick and albuminuria by ELISA, and monocyte depletion had no effect. However, monocyte depletion significantly reduced glomerular necrosis and crescent formation (21.4±10.5 vs. 4.3±2.2 for crescents and 12.0±7.1 vs. 3.0±1.1 for necrosis, p<0.05 for both) and abrogated monocyte, macrophage and dendritic cell increase in the affected kidneys, whereas renal neutrophil numbers were not affected. Soluble CD163 increased in serum, but not in urine with anti-MPO antibody treatment and was completely abolished with monocyte depletion.

Conclusion

Our findings provide novel experimental evidence that monocytes are important disease contributors in ANCA-mediated NCGN. Whereas neutrophils are sufficient to induce nephritic urine abnormalities, albuminuria, and some NCGN, inflammatory monocytes clearly enhanced necrosis and crescent formation.

Funding

  • Government Support - Non-U.S.