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P067 Il-17 resulting from cell interactions during chronic inflammation: comparison between joint-derived- and skin-derived-mesenchymal cells
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  1. M Noack,
  2. P Miossec

Abstract

Immunogenomic and Inflammation Unit, Hospital Edouard Herriot, University Claude Bernard Lyon 1, Lyon, France

Introduction IL-17, mainly produced by Th17 cells, is a major pro-inflammatory cytokine involved in several chronic inflammatory diseases. Furthermore, during chronic inflammation, immune cells, notably Th17 cells, migrate to the inflammatory site, synovium or skin for example, and interact with the local mesenchymal cells (synoviocytes or skin fibroblasts).

Objectives The aim is to study and compare the effect of cellular interactions between immune cells and mesenchymal cells (MC) from different origins on pro-inflammatory cytokine production, with a focus on IL-17, and to identify the involved mechanisms.

Methods A co-culture system with MC (synoviocytes or skin fibroblasts) and PBMC was developed. MC were cultured overnight and PBMC were seeded at a 5:1 ratio for 48 hour, in the presence or not of TCR activation with PHA. Transwell system was used to study cell-cell contact. Monocytes were removed to study their involvement. An antibody against podoplanin was pre-incubated with PBMC before co-culture. Supernatants were collected at 48 hour and IL-6, IL-1β and IL-17 production measured by ELISA. Extracellular (CD3, CD4) and intracellular (IL-17) staining of PBMC was analysed by flow cytometry.

Results In control conditions, IL-6 and IL-1β production was increased more than 20 fold and 10 fold respectively, in PBMC-MC co-culture compared to PBMC alone (p≤0.05). No additional effect was observed with PBMC activation. Flow cytometry showed no significant difference in the percentage of Th17 cells in activated-PBMC alone or co-cultured with MC (p=0.4). Conversely, IL-17 production was highly increased at least 10 fold only in co-cultures with activated-PBMC (p≤0.02). Transwell experiments confirm that cell-cell contact was critical for IL-17 secretion. The removal of monocytes highly decreased the IL-1β production by 80%–90% (p≤0.05) with both MC, while the IL-17 secretion was decreased with skin fibroblasts by 60% but not with synoviocytes. The inhibition of podoplanin, interaction molecule involved in the modulation of IL-8 secretion during synoviocyte-platelet interactions, was tested. The addition of an anti-podoplanin antibody decreased significantly IL-17 secretion by 60%, similarly with skin fibroblasts and synoviocytes.

Conclusions Cellular interactions between mesenchymal cells and immune cells play a major role in the pro-inflammatory cytokine production, leading to a heightened IL-17 secretion. The podoplanin molecule seems play a crucial role in this mechanism. Nevertheless, the inhibition of IL-17 remains only partial that means podoplanin is one of the involved mechanisms but others have to be identified.

Disclosure of interest None declared

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