ISR Autumn Meeting 2016

Joint Winner - Young Investigator Award 2016

Dr Mary Canavan
Department of Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland

Oral (16A150)

CD141+ DC are enriched in the inflamed synovium of Rheumatoid Arthritis patients and induce both CD4+ and CD8+ T cell responses

Author(s)

Mary Canavan1, Barry Moran2, Carl Orr3, Ronan Mullen3, Jean Fletcher2, Douglas Veale3 and Ursula Fearon1

Department(s)/Institutions

1Department of Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland. 2School of Biochemistry & Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland. 3Translational Rheumatology Research Group, Dublin Academic Medical Centre, St. Vincent’s University Hospital, Dublin, Ireland. 4Department of Rheumatology, Adelaide and Meath Hospital, Dublin, Ireland.

Introduction

Dendritic cells (DC) are a heterogeneous group of antigen presenting cells. Currently their classification within blood & skin has been well characterised however their identification within other tissues, in particular in the context of autoimmunity is limited. CD141 DC in particular have yet to be identified in RA and it is unknown what role they may play in the pathogenesis of the disease.

Aims/Background

The aim of this work was to identify DC within the inflamed synovium and determine if these DC are phenotypically and functionally distinct from their blood counterparts.

Method

Synovial tissue was digested to yield a single cell suspension which was subsequently stained with a panel of antibodies & analysed by multicolour flow cytometry. PBMC/SFMC were isolated from blood or fluid using a density-gradient separation & stained with DC specific markers for flow cytometry analysis. DC were sorted from SFMC & cocultured with T cells. T cells were intracellularly stained with antibodies specific for T cell related cytokines. Finally, supernatants from DC-T cell cocultures were used to treat a normal synoviocyte cell line & the expression of adhesion molecules was measured.

Results

mDC are significantly decreased in RA blood compared to HC (p<0.05), suggesting DC are recruited to the site of inflammation. There is a significant increase in the frequency of DC within the synovial tissue of RA patients compared to matched blood (p<0.05) These DC have a more activated phenotype with a significant increase in CD80(p<0.001) & CD40(p<0.05) expression compared to blood DC. DC can be subdivided into different subsets, one of which, the CD141 DC has never been described in RA. CD141 DC were discovered in 2010 & little is known about their function in health & indeed disease. We can report that CD141 DC are significantly enriched in RA synovial fluid (SF) compared CD141 DC found in blood (p<0.001). SF CD141 DC express higher levels of CD80, CD86 and CD40 compared to blood DC. CD141 DC induce both CD4 and CD8 proliferation. In addition to this, SF CD141 DC induce a strong CD8 response - as seen by the production of Granzyme B. SF CD141 DC also induce TNFα, IFNγ and GMCSF from CD4 T cells. Finally, synovial fibroblasts play a key role in mediating damage in the RA joint; therefore we examined the effect of this CD141-T cell interaction on fibroblast activation. Supernatants from CD141 activated T cells were cultured with fibroblasts & induced expression of the adhesion molecule ICAM-1

Conclusions

The novel DC population, CD141 DC are significantly enriched in the RA joint & display heightened expression of activation markers compared to their blood counterparts. These cells are capable of inducing both CD4 & CD8 T cell responses and can subsequently activate synovial fibroblasts. This data suggests that CD141 DC may orchestrate a number of inflammatory processes that can occur in the inflamed joint.

Image 1