Synovial CD4+ T-cell-derived GM-CSF supports the differentiation of an inflammatory dendritic cell population in rheumatoid arthritis.
OBJECTIVE
A population of synovial inflammatory dendritic cells (infDCs) has recently been identified in rheumatoid arthritis (RA) and is thought to be monocyte-derived. Here, we investigated the role and source of granulocyte macrophage-colony-stimulating factor (GM-CSF) in the differentiation of synovial infDC in RA.


METHODS
Production of GM-CSF by peripheral blood (PB) and synovial fluid (SF) CD4+ T cells was assessed by ELISA and flow cytometry. In vitro CD4+ T-cell polarisation experiments were performed with T-cell activating CD2/CD3/CD28-coated beads in the absence or presence of pro-Th1 or pro-Th17 cytokines. CD1c+ DC and CD16+ macrophage subsets were flow-sorted and analysed morphologically and functionally (T-cell stimulatory/polarising capacity).


RESULTS
RA-SF CD4+ T cells produced abundant GM-CSF upon stimulation and significantly more than RA-SF mononuclear cells depleted of CD4+ T cells. GM-CSF-producing T cells were significantly increased in RA-SF compared with non-RA inflammatory arthritis SF, active RA PB and healthy donor PB. GM-CSF-producing CD4+ T cells were expanded by Th1-promoting but not Th17-promoting conditions. Following coculture with RA-SF CD4+ T cells, but not healthy donor PB CD4+ T cells, a subpopulation of monocytes differentiated into CD1c+ infDC; a process dependent on GM-CSF. These infDC displayed potent alloproliferative capacity and enhanced GM-CSF, interleukin-17 and interferon-γ production by CD4+ T cells. InfDC with an identical phenotype to in vitro generated cells were significantly enriched in RA-SF compared with non-RA-SF/tissue/PB.


CONCLUSIONS
We demonstrate a therapeutically tractable feedback loop of GM-CSF secreted by RA synovial CD4+ T cells promoting the differentiation of infDC with potent capacity to induce GM-CSF-producing CD4+ T cells.
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
G
G
Reynolds
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
J R
JR
Gibbon
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
A G
AG
Pratt
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
M J
MJ
Wood
Sunderland Royal Hospital, Sunderland, UK.
D
D
Coady
Sunderland Royal Hospital, Sunderland, UK.
G
G
Raftery
Department of Rheumatology, Freeman Hospital, Newcastle-Upon-Tyne, UK.
A R
AR
Lorenzi
Department of Rheumatology, Freeman Hospital, Newcastle-Upon-Tyne, UK.
A
A
Gray
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Rheumatology Research Group, MRC Centre for Immune Regulation, School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
A
A
Filer
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Rheumatology Research Group, MRC Centre for Immune Regulation, School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
C D
CD
Buckley
Haematological Sciences, Institute of Cellular Medicine, Newcastle University, Newcastle-Upon-Tyne, UK.
M A
MA
Haniffa
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
J D
JD
Isaacs
Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence Musculoskeletal Research Group, Newcastle University, Newcastle-Upon-Tyne, UK.
C M U
CM
Hilkens
D018949:Antigens, CD1 / Q000032:analysis; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018920:Coculture Techniques; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000276:immunology*; D006023:Glycoproteins / Q000032:analysis; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008264:Macrophages / Q000276:immunology; D009000:Monocytes / Q000276:immunology; D010003:Osteoarthritis / Q000276:immunology; D013582:Synovial Fluid / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology
D018949:Antigens, CD1; C437944:CD1C protein, human; D016207:Cytokines; D006023:Glycoproteins; D018950:Lipopolysaccharide Receptors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor
Autoimmunity; Cytokines; Inflammation; Rheumatoid Arthritis; T Cells