Interleukin-15 induces interleukin-17 production by synovial T cell lines from patients with rheumatoid arthritis.

IL-17-producing T cells (Th17 cells) are believed to contribute to local inflammation and joint damage in rheumatoid arthritis (RA). Limited data exist on Th17 cells located within the inflamed synovial tissue (ST) of patients with RA. Here, we aimed to generate polyclonal T cell lines (TCLs) from the RA ST and assess their cytokine production, including the effects of exogenous IL-15 on IL-17 production in vitro. For five patients with RA, polyclonal TCLs were established from ST obtained by joint surgery. Synovial TCLs were expanded and stimulated by anti-CD3/CD28 microbeads and exogenous cytokines. Cytokine production was assessed by culture supernatant analyses and intracellular flow cytometry, and TCLs were sorted based on their surface expression of CCR6. In addition to IL-17, we detected IL-6, IL-10, IFN-γ and TNF-α in the synovial TCL culture supernatants. Exogenous IL-15 increased the production of IL-17 as well as the other cytokines except IFN-γ. For IL-17, this effect was more pronounced after prolonged culture times. Intracellular flow cytometry confirmed the presence of IL-17+ and IL-17+ IFN-γ+ CD4+ T cells in the TCLs. IL-17+ and IL-17+ IFN-γ+ T cells were enriched in the CD4+ CCR6+ population. In conclusion, Th17 cells can be detected after polyclonal expansion and stimulation of RA synovial TCLs generated by joint surgery. The Th17 cells from the RA ST were enriched in the CD4+ CCR6+ population, and they were sensitive to exogenous IL-15. Th17 cells present within the synovial compartment may contribute to the RA pathogenesis and local joint damage.

Serum IgG antibodies to peptidylarginine deiminase 4 predict radiographic progression in patients with rheumatoid arthritis treated with tumour necrosis factor-alpha blocking agents.

BACKGROUND: Peptidylarginine deiminase 4 (PAD4) may generate epitopes targeted by anticitrullinated protein antibodies in rheumatoid arthritis (RA). A subset of patients with RA has serum autoantibodies to human recombinant PAD4 (hPAD4). Here, we assessed whether anti-hPAD4 status in RA predicted disease outcome after antitumour necrosis factor (anti-TNF)-alpha therapy. METHODS: We analysed RA sera obtained at baseline (n = 40) and after 1 year on anti-TNF-alpha therapy (n = 33) for anti-hPAD4 IgG. Association analyses between baseline anti-hPAD status and disease progression were performed. RESULTS: We found that 17 of 40 patients (42.5%) were serum anti-hPAD4 positive at baseline, and the anti-hPAD4 IgG levels were stable over 1 year on anti-TNF-alpha therapy. At baseline, there were indications that anti-hPAD4 positive patients had more severe disease than the negative patients. After 1 year on anti-TNF-alpha therapy, the anti-hPAD4 positive patients displayed a persistently elevated disease activity score using 28 joint counts score and increased progression in the van der Heijde-modified Sharp erosion score. Accordingly, more anti-hPAD4 positive than negative patients presented an increase in van der Heijde-modified Sharp erosion scores >0 over 1 year. CONCLUSIONS: Anti-hPAD4 IgG can be detected in a subset of RA sera and the levels are stable after initiation of anti-TNF-alpha therapy. Serum anti-hPAD4 may predict persistent disease activity and radiographic progression in patients with RA receiving anti-TNF-alpha therapy.

Serum IgG antibodies to peptidylarginine deiminase 4 in rheumatoid arthritis and associations with disease severity.

BACKGROUND: Antibodies targeting citrullinated antigens are specific for rheumatoid arthritis (RA). Citrullination is catalysed by the peptidylarginine deiminase (PAD) enzyme family. Critical enzymes are often targeted by disease-specific antibodies in complex immune-mediated diseases. Here, we have tested for autoantibodies against human recombinant PAD4 (hPAD4) in Caucasian RA patients. METHODS: A time-resolved fluorometric immunoassay based on hPAD4 was developed to analyse sera from two RA cohorts (n = 237 and n = 177), one systemic lupus erythaematosus (SLE) cohort (n = 84) and 148 healthy controls. Simple and multiple analyses were performed to examine possible associations between anti-hPAD4 and disease variables. RESULTS: Raised levels of anti-hPAD4 IgG were found in both RA cohorts compared to the controls, and 23% of the RA patients were anti-hPAD4 IgG positive. Anti-hPAD4 was associated with anti-cyclic citrullinated peptide (CCP) and rheumatoid factor (RF), as well as increased physical disability. Anti-hPAD4 was also associated with higher longitudinal radiographic damage scores and increased clinical joint pathology, but weaker than anti-CCP. No associations were found between anti-hPAD4 and selected Human leukocyte antigen (HLA)-DRB1 variants. CONCLUSIONS: Approximately 23% of Caucasian RA patients have serum IgG antibodies against hPAD4. The presence of serum anti-hPAD4 IgG was in simple analyses associated with a more severe disease phenotype, and the association with physical disability was maintained in multiple analyses.