89. The role of monocyte subsets and CSF2 in the pathogenesis of ANCA-induced glomerulonephritis
Creators: name: Rousselle1, Anthony
name: Mildner2, Alexander
name: Sonnemann1, Janis
name: Doerte Lodka1
name: Amann5, Kerstin
name: Bieringer3, Markus
name: Schneider4, Udo
name: Kettritz1, Ralph
name: Leutz2, Achim
name: Enghard1, Phillip
name: Schreiber1, Adrian
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background</strong>: Activation of myeloid cells by circulating anti-neutrophil cytoplasmic autoantibodies (ANCA) is essential in the development of ANCA –associated vasculitis (AAV) and necrotizing crescentic glomerulonephritis (NCGN). In contrast to neutrophils, the contribution of classical and non-classical monocyte subsets in AAV remains poorly described. Classical monocytes are released from the bone marrow into circulation where they can differentiate into non-classical monocytes. This differentiation is under the control of the CCAAT/enhancer binding protein β (C/EBPβ) transcription factor. Colony stimulating factor 2 (CSF2) is a cytokine which stimulates stem cells to produce myeloid cells. Recent studies have put in evidence that high level of CSF2 is present in patients with autoimmune diseases and is an important pathogenic factor by modulating monocyte functions. Our work aimed to investigate the contribution of both monocyte subsets and the involvement of CSF2 in ANCA-associated NCGN. <strong>Methods</strong>: To assess the differential role of both monocyte subsets, myeloperoxidase<sup>-/-</sup> (MPO<sup>-/-</sup>) mice were immunized with murine MPO, irradiated and subsequently transplanted with hematopoietic cells from either WT, CCR2<sup>-/-</sup> or C/EBPβ<sup>-/-</sup> mice. Mice were sacrificed and examined 6-8 weeks following transplantation. CSF2 expression was studied in kidney and urine of mice with AAV and was used <em>in vitro</em> for the stimulation of human and murine monocytes. The contribution of CSF2 <em>in vivo</em> was investigated in MPO<sup>-/-</sup> mice transplanted with bone marrow cells from CSF2rb<sup>-/-</sup> mice following the procedure described above. Finally, we quantified urinary monocytes and CSF2 levels in patients with AAV. <strong>Results</strong>: CCR2<sup>-/-</sup> chimeric mice showed a reduction in circulating Ly6C<sup>hi</sup> classical monocytes and were protected from the development of renal damage compared to WT chimeric mice. In contrast, C/EBPβ<sup>-/-</sup> chimeric mice lacking non-classical monocytes developed glomerular necrosis and crescent formation to the same extend as WT chimeric mice. Kidney and urinary CSF2 protein levels were upregulated in mice with AAV. <em>In vitro</em>, CSF2 increased the ability of ANCA-stimulated monocytes to release interleukin-1β (IL1-β) and induce the polarization of CD4<sup>+</sup> T-cells into T helper 17 (T<sub>H</sub>17) effector cells. CSF2rb<sup>-/-</sup> chimeric mice were protected from glomerulonephritis and exhibited reduced numbers of kidney T<sub>H</sub>17 cells. Finally, we found increased numbers of both urinary classical monocytes and CSF2 levels in patients with active kidney AAV. In addition, kidney CSF2 expression was also increased in these patients. <strong>Conclusions</strong>: Classical, but not non-classical, monocytes are important mediators of renal damage in AAV. CSF2 is a crucial pathological factor in AAV by modulating monocyte pro-inflammatory functions. Classical monocytes and CSF2 levels were increased in urine from patients with AAV. Our data suggest that monocytes and CSF2 might represent novel interesting therapeutic targets. <strong>Disclosures</strong>: none