Signalling profiles of circulating leucocytes in patients recovered from reactive arthritis.

OBJECTIVES: Reactive arthritis (ReA) is a sterile joint inflammation triggered by a remote infection and associated with human leucocyte antigen (HLA)-B27. Its pathogenesis is unknown, but abnormal response to microbial structures or endogenous inflammatory mediators may be involved. We studied responses in leucocyte signalling profiles in patients with previous ReA after a full recovery. METHOD: The study comprised 10 HLA-B27-positive healthy subjects with a history of Yersinia enterocolitica-triggered ReA (B27+ReA+) and 20 healthy reference subjects, of whom 10 carried HLA-B27 (B27+ReA-) and 10 did not (B27-ReA-). Phosphospecific fluorescent monoclonal antibodies and flow cytometry were used to determine activation of nuclear factor kappa B (NF-κB), signal transducers and activators of transcription (STATs) 1, 3, 5, and 6, and two mitogen-activated protein (MAP) kinases, p38 and extracellular signal-regulated kinase (ERK)1/2, in monocytes, lymphocytes, lymphocyte subsets, and neutrophils. B27+ReA+ and B27-ReA- whole-blood samples were incubated with Yersinia with or without infliximab to study the role of tumour necrosis factor (TNF) in lymphocyte subset activation. Samples of the three subject groups were studied using soluble bacterial or endogenous stimuli. Fluorescence levels were determined as relative fluorescence units (RFU) and the proportion of positively fluorescing cells. RESULTS: The intracellular activation of circulating leucocytes in response to soluble stimuli was consistently comparable in B27+ReA+, B27+ReA-, and B27-ReA- subjects. Infliximab inhibited Yersinia-induced lymphocyte NF-κB phosphorylation similarly in B27+ReA+ and B27-ReA- groups. CONCLUSIONS: ReA susceptibility is not reflected in leucocyte signalling profiles elicited by phlogistic stimuli. However, the possibility remains that aberrations occur in response to combinations of stimuli, such as those associated with leucocyte adhesion.

Expression of IL-10 family cytokines in rheumatoid arthritis: elevated levels of IL-19 in the joints.

OBJECTIVES: Interleukin (IL)-10 functions as an anti-inflammatory cytokine in rheumatoid arthritis (RA). New IL-10 family cytokines IL-19, IL-20, IL-22, IL-24, and IL-26 have recently been discovered. Information concerning the expression and function of these cytokines in autoimmune diseases is currently limited. The aim of this study was to investigate their expression in RA. METHODS: mRNA levels of the cytokines were studied using quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Peripheral blood (PB) and synovial fluid (SF) mononuclear cells (MCs), purified T cells, and monocytes/macrophages from RA patients and healthy volunteers, and synovial tissues from patients with RA or osteoarthritis (OA), were examined. The expression of IL-19 protein in T cells and monocytes/macrophages was studied by flow cytometry. RESULTS: IL-10 and IL-19 mRNA levels were significantly elevated in SFMCs from patients with RA compared with PBMCs from RA patients or healthy volunteers. IL-20 and IL-22 mRNA levels were also upregulated in RA SFMCs but their level of expression was lower than that of IL-10 or IL-19. Importantly, synovial tissue IL-19 levels in RA were increased when compared with OA. IL-19 expression was upregulated in both T cells and macrophages derived from patients with RA. IL-1beta increased IL-19 levels in PBMCs, suggesting that elevated levels of IL-1 in RA joints may contribute to upregulated IL-19 expression. CONCLUSIONS: The majority of the IL-10 family cytokines are expressed in RA. IL-19 demonstrated the highest expression in rheumatoid joints, and could thus be involved in the regulation of synovial inflammation in RA.

The expression of SOCS is altered in rheumatoid arthritis.

OBJECTIVES: Cytokines play a key pathogenic role in rheumatoid arthritis (RA). Several cytokines signal through the JAK-STAT pathway, which is negatively regulated by the suppressors of cytokine signalling (SOCS) proteins. Since SOCS protein levels can profoundly modulate cellular responses to cytokines, we have investigated their expression in chronic RA. METHODS: The levels of SOCS1-3 and CIS1 mRNA in peripheral blood (PB) and synovial fluid (SF) mononuclear cells (MCs), purified T cells and monocytes from RA patients and healthy volunteers were studied using quantitative reverse transcriptase polymerase chain reaction (RT-PCR). SOCS mRNA and protein expression in synovial tissues were examined by RT-PCR and immunohistochemistry. RESULTS: The levels of SOCS1 and SOCS3 were significantly increased in PBMCs from RA patients when compared with healthy volunteers. These differences were mainly due to up-regulation of SOCS1 in PB T cells and of SOCS3 in PB monocytes. In addition, SOCS2 was up-regulated in PB T cells. Interestingly, SF T cells expressed lower and SF macrophages higher levels of SOCS molecules than their PB counterparts. Similarly, while a significant portion of macrophages in synovial tissues expressed SOCS1 and SOCS3 proteins, the majority of T cells remained SOCS negative. Finally, SOCS1 was up-regulated in the synovial membranes from patients with RA when compared with osteoarthritis. CONCLUSIONS: SOCS expression levels are profoundly altered in RA, and the profile of SOCS expression is dependent on both the cell type as well as the cellular compartment.