ObjectiveTo determine the prevalence of upregulation of interferon (IFN) type I inducible genes, the so called ‘IFN type I signature’, in CD14 monocytes in 69 patients with primary Sjögren's syndrome (pSS) and 44 healthy controls (HC) and correlate it with disease manifestations and expression of B cell activating factor (BAFF).MethodsExpression of IFI44L, IFI44, IFIT3, LY6E and MX1 was measured using real time quantitative PCR in monocytes. Expression values were used to calculate IFN type I scores for each subject. pSS patients positive for the IFN type I signature (IFN score≥10) and patients negative for the signature (IFN score<10) were then compared for clinical disease manifestations and BAFF expression. A bioassay using a monocytic cell line was performed to study whether BAFF mRNA expression was inducible by IFN type I activity in serum of patients with pSS.ResultsAn IFN type I signature was present in 55% of patients with pSS compared with 4.5% of HC. Patients with the IFN type I signature showed: (a) higher EULAR Sjögren's Syndrome Disease Activity Index scores; higher anti-Ro52, anti-Ro60 and anti-La autoantibodies; higher rheumatoid factor; higher serum IgG; lower C3, lower absolute lymphocyte and neutrophil counts; (b)higher BAFF gene expression in monocytes. In addition, serum of signature-positive patients induced BAFF gene expression in monocytes.ConclusionsThe monocyte IFN type I signature identifies a subgroup of patients with pSS with a higher clinical disease activity together with higher BAFF mRNA expression. Such patients might benefit from treatment blocking IFN type I production or activity.

An IFN type I signature is observed in patients with SSc from the earliest phases of the disease, even before overt skin fibrosis. The presence of IFN type I signature in monocytes is correlated with BAFF mRNA expression and serum PIIINP levels, supporting a contribution in the pathogenesis and progression of SSc.

ObjectiveTo establish an easy and practical assay for identifying systemic interferon (IFN) type I bioactivity in patients with primary Sjögren's syndrome (pSS). The IFN type I signature is present in over half of the pSS patients and identifies a subgroup with a higher disease activity. This signature is currently assessed via laborious expression profiles of multiple IFN type I-inducible genes.MethodsIn a cohort of 35 pSS patients, myxovirus-resistance protein A (MxA) was assessed as a potential biomarker for type I IFN activity, using an enzyme immunoassay (EIA) on whole-blood and flow cytometric analyses (fluorescence-activated cell sorting, FACS) of isolated CD14 monocytes. In addition, potential biomarkers such as CD64, CD169 and B cell-activating factor (BAFF) were simultaneously analysed in CD14 monocytes using FACS. The IFNscore, a measure for total type I IFN bioactivity, was calculated using expression values of the IFN type I signature genes—IFI44, IFI44L, IFIT3, LY6E and MX1—in CD14 monocytes, determined by real-time quantitative PCR.ResultsIFNscores correlated the strongest with monocyte MxA protein (r=0.741, p<0.001) and whole-blood MxA levels (r=0.764, p<0.001), weaker with CD169 (r=0.495, p<0.001) and CD64 (r=0.436, p=0.007), and not at all with BAFF protein. In particular, whole blood MxA levels correlated with EULAR Sjögren's Syndrome Disease Activity Index scores and numerous clinical pSS parameters. Interestingly, patients on hydroxychloroquine showed reduced MxA levels (EIA, p=0.04; FACS p=0.001).ConclusionsThe MxA assays were excellent tools to assess IFN type I activity in pSS, MxA-EIA being the most practical. MxA levels associate with features of active disease and are reduced in hydroxychloroquine-treated patients, suggesting the clinical applicability of MxA in stratifying patients according to IFN positivity.

Here we conclude a contrasting expression pattern of the RNA-sensing receptors TLR7, RIG-I and MDA5 in pDCs and monocytes of patients with IFNpos pSS. This profile could explain the pathogenic IFN production and might reveal novel therapeutic targets in these patients.

Objective. Indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme that converts tryptophan to kynurenine, is driven in part by type I and type II interferons (IFNs). Naive T cells are polarized into FoxP31 Treg cells upon exposure to either IDO1 cells or kynurenine. Recent studies have suggested that the kynurenine pathway reflects a crucial interface between the immune and nervous system. The aims of the present study were to evaluate whether Treg cell levels are elevated, in conjunction with increased IDO activity, in patients with primary Sj€ ogren's syndrome (SS) who are positive for the IFN gene expression signature, and to investigate the downstream kynurenine pathway in these patients.Methods. Serum from 71 healthy controls, 58 IFNnegative patients with primary SS, and 66 IFN-positive patients with primary SS was analyzed using highperformance liquid chromatography to measure the levels of tryptophan and kynurenine. Expression levels of messenger RNA (mRNA) for IDO and downstream enzymes in the kynurenine pathway were assessed in CD141 monocytes using real-time quantitative polymerase chain reaction. CD41CD45RO1 T helper memory cell populations were analyzed by flow cytometry.Results. Significantly increased levels of IDO activity (assessed as the kynurenine:tryptophan ratio) (P 5 0.0054) and percentages of CD25 high FoxP31 Treg cells (P 5 0.039) were observed in the serum from IFN-positive patients with primary SS, and these parameters were significantly correlated with one another (r 5 0.511, P 5 0.002). In circulating monocytes from IFN-positive patients with primary SS, the expression of IDO1 mRNA was up-regulated (P < 0.0001), and this was correlated with the IFN gene expression score (r 5 0.816, P < 0.0001). Interestingly, the proapoptotic and neurotoxic downstream enzyme kynurenine 3-monooxygenase was up-regulated (P 5 0.0057), whereas kynurenine aminotransferase I (KATI) (P 5 0.0003), KATIII (P 5 0.016), and KATIV (P 5 0.04) were down-regulated in IFN-positive patients with primary SS compared to healthy controls.Conclusion. These findings demonstrate enhanced IDO activity in conjunction with increased percentages of CD25 high FoxP31 Treg cells in primary SS patients who carry the IFN signature. In addition, IFN-positive patients with primary SS exhibit an imbalanced kynurenine pathway, with evidence of a shift toward potentially more proapoptotic and neurotoxic metabolites. Intervening in these IFN-and IDO-induced immune system imbalances may

IntroductionA hallmark of systemic autoimmune diseases like systemic lupus erythematosus (SLE) is the increased expression of interferon (IFN) type I inducible genes, so-called IFN type I signature. Recently, T-helper 17 subset (Th17 cells), which produces IL-17A, IL-17F, IL-21, and IL-22, has been implicated in SLE. As CCR6 enriches for Th17 cells, we used this approach to investigate whether CCR6+ memory T-helper cells producing IL-17A, IL-17F, IL-21, and/or IL-22 are increased in SLE patients and whether this increase is related to the presence of IFN type I signature.MethodsIn total, 25 SLE patients and 15 healthy controls (HCs) were included. SLE patients were divided into IFN type I signature-positive (IFN+) (n = 16) and negative (IFN-) (n = 9) patients, as assessed by mRNA expression of IFN-inducible genes (IFIGs) in monocytes. Expression of IL-17A, IL-17F, IL-21, and IL-22 by CD4+CD45RO+CCR6+ T cells (CCR6+ cells) was measured with flow cytometry and compared between IFN+, IFN- patients and HCs.ResultsIncreased percentages of IL-17A and IL-17A/IL-17F double-producing CCR6+ cells were observed in IFN+ patients compared with IFN- patients and HCs. IL-17A and IL-17F expression within CCR6+ cells correlated significantly with IFIG expression. In addition, we found significant correlation between B-cell activating factor of the tumor necrosis family (BAFF)–a factor strongly correlating with IFN type I - and IL-21 producing CCR6+ cells.ConclusionsWe show for the first time higher percentages of IL-17A and IL-17A/IL-17F double-producing CCR6+ memory T-helper cells in IFN+ SLE patients, supporting the hypothesis that IFN type I co-acts with Th17 cytokines in SLE pathogenesis.

Incomplete dRTA is common in pSS and causes mild acidaemia and higher urinary pH, which may contribute to bone demineralization and kidney stone formation. FF cannot replace NH4Cl in testing urinary acidification in pSS, but may be considered as a screening tool, given its reasonable negative predictive value and better tolerability.

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by lymphocytic infiltrates in salivary and lacrimal glands. Clinical manifestations range from ocular and oral dryness to vasculitis and severe fatigue. pSS is a disease with heterogeneous symptoms and a variable response to the available treatment. Recently, a key role for Interferon (IFN) type I has been implicated in the pathogenesis of pSS. As type I IFN consists of 17 different subtypes, it cannot be easily assessed using a conventional ELISA. Therefore the expression of type I IFN inducible genes--the so-called type I IFN signature--is assessed in salivary gland tissue and blood from patients as a readout for type I IFN activity. In this review we discuss the potential of type I IFN as a novel biomarker for disease activity, subclassification of patients, prediction of therapy response and most importantly as a target for therapeutic intervention.