Divergent Roles of Rheumatoid Arthritis Synovial Dendritic Cells


Mary Canavan 1, Viviana Marzalioli 1, Vipul Bhargava 2, Ronan Mullan 3, Douglas J Veale 4, Ursula Fearon 1


1 Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin. 2 Janssen Research & Development, Spring House, Pennsylvania, USA 3 Department of Rheumatology, Adelaide and Meath Hospital, Dublin 4 Centre for Arthritis and Rheumatic Diseases, St Vincents University Hospital, Dublin


Dendritic Cells (DC) are potent antigen presenting cells which can be subdivided into CD141
and CD1c DC. We reported a previously unacknowledged role of CD141 + DC in the RA
synovium however, the identification and function of CD1c + in RA has yet to be fully


To investigate if CD1c + DC are present in the RA synovium and if they are transcriptionally and functionally distinct to synovial CD141 + DC.


Synovial biopsies were obtained via arthroscopy and enzymatically and
mechanically dissociated to yield a single cell suspension. Synovial fluid mononuclear cells
(SFMC) and peripheral blood mononuclear cells (PBMC) in addition to synovial tissue digests
were stained with a panel of fluorochrome conjugated antibodies and analysed by
multicolour flow cytometry. CD1c + DC and CD141 + DC were magnetically sorted from RA
synovial fluid and cocultured with allogeneic CTV labelled T cells. Finally, RNA sequencing
was performed on sorted synovial CD1c and CD141 DC and downstream bioinformatic
analysis was performed.


A distinct population of CD1c+ DC were identified in the RA synovium with high
expression of DC maturation markers CD80 and CD40. CD1c + DC express high levels of the
chemokine receptors CCR7 and CXCR4 suggestive of increased
migration of DC to the joint. Furthermore, upon examination of peripheral blood and
synovial fluid CD1c + DC, we demonstrate increased frequencies of CD1c + DC in the synovium
compared to peripheral blood. Synovial CD1c + DC are transcriptionally distinct from synovial
CD141 + DC as identified but Principal component analysis (PCA) and hierarchical clustering
analysis. Moreover, IPA analysis revealed that pathways involved in T cell activation, T cell
exhaustion and DC maturation were upregulated in synovial CD1c + DC compared to
CD141 + DC. Following coculture of allogeneic T cells with either synovial CD1c + DC or
CD141 + DC we noted a preferential induction of CD4 + T cell derived GMCSF, TNFα and IFNƴ in
CD1c + DC cocultures. However, CD141 + DC were superior in induction of a TNFα producing
CD8 + T cell population.


Mature CD1c DC are enriched in the RA joint and are transcriptionally distinct
from synovial CD141+DC. Synovial DC may play distinct roles in RA pathology via differential
T cell activation.