Longitudinal analysis of T-cell receptor repertoires reveals persistence of antigen-driven CD4+ and CD8+ T-cell clusters in systemic sclerosis.

The T-cell receptor (TCR) is a highly polymorphic surface receptor that allows T-cells to recognize antigenic peptides presented on the major histocompatibility complex (MHC). Changes in the TCR repertoire have been observed in several autoimmune conditions, and these changes are suggested to predispose autoimmunity. Multiple lines of evidence have implied an important role for T-cells in the pathogenesis of Systemic Sclerosis (SSc), a complex autoimmune disease. One of the major questions regarding the roles of T-cells is whether expansion and activation of T-cells observed in the diseases pathogenesis is antigen driven. To investigate the temporal TCR repertoire dynamics in SSc, we performed high-throughput sequencing of CD4+ and CD8+ TCRß chains on longitudinal samples obtained from four SSc patients collected over a minimum of two years. Repertoire overlap analysis revealed that samples taken from the same individual over time shared a high number of TCRß sequences, indicating a clear temporal persistence of the TCRß repertoire in CD4+ as well as CD8+ T-cells. Moreover, the TCRßs that were found with a high frequency at one time point were also found with a high frequency at the other time points (even after almost four years), showing that frequencies of dominant TCRßs are largely consistent over time. We also show that TCRß generation probability and observed TCR frequency are not related in SSc samples, showing that clonal expansion and persistence of TCRßs is caused by antigenic selection rather than convergent recombination. Moreover, we demonstrate that TCRß diversity is lower in CD4+ and CD8+ T-cells from SSc patients compared with memory T-cells from healthy individuals, as SSc TCRß repertoires are largely dominated by clonally expanded persistent TCRß sequences. Lastly, using "Grouping of Lymphocyte Interactions by Paratope Hotspots" (GLIPH2), we identify clusters of TCRß sequences with homologous sequences that potentially recognize the same antigens and contain TCRßs that are persist in SSc patients. In conclusion, our results show that CD4+ and CD8+ T-cells are highly persistent in SSc patients over time, and this persistence is likely a result from antigenic selection. Moreover, persistent TCRs form high similarity clusters with other (non-)persistent sequences that potentially recognize the same epitopes. These data provide evidence for an antigen driven expansion of CD4+/CD8+ T-cells in SSc.

Fatty Acid and Carnitine Metabolism Are Dysregulated in Systemic Sclerosis Patients.

Systemic sclerosis (SSc) is a rare chronic disease of unknown pathogenesis characterized by fibrosis of the skin and internal organs, vascular alteration, and dysregulation of the immune system. In order to better understand the immune system and its perturbations leading to diseases, the study of the mechanisms regulating cellular metabolism has gained a widespread interest. Here, we have assessed the metabolic status of plasma and dendritic cells (DCs) in patients with SSc. We identified a dysregulated metabolomic signature in carnitine in circulation (plasma) and intracellularly in DCs of SSc patients. In addition, we confirmed carnitine alteration in the circulation of SSc patients in three independent plasma measurements from two different cohorts and identified dysregulation of fatty acids. We hypothesized that fatty acid and carnitine alterations contribute to potentiation of inflammation in SSc. Incubation of healthy and SSc dendritic cells with etoposide, a carnitine transporter inhibitor, inhibited the production of pro-inflammatory cytokines such as IL-6 through inhibition of fatty acid oxidation. These findings shed light on the altered metabolic status of the immune system in SSc patients and opens up for potential novel avenues to reduce inflammation.

Novel insights into dendritic cells in the pathogenesis of systemic sclerosis.

Systemic sclerosis (SSc) is a severe autoimmune fibrotic disease characterized by fibrosis, vasculopathy, and immune dysregulation. Dendritic cells (DCs) are the most potent antigen-presenting cells, specialized in pathogen sensing, with high capacity to shape the immune responses. The most recent technological advances have allowed the discovery of new DC subsets with potential implications in inflammatory conditions. Alterations of DC distribution in circulation and affected tissue as well as impaired DC function have been described in SSc patients, pointing towards a crucial role of these cells in SSc pathogenesis. In particular, recent studies have shown the importance of plasmacytoid DCs either by their high capacity to produce type I interferon or other inflammatory mediators implicated in SSc pathology, such as chemokine C-X-C motif ligand 4 (CXCL4). In-vivo models of SSc have been vital to clarify the implications of DCs in this disease, especially DCs depletion and specific gene knock-down studies. This review provides these new insights into the contribution of the different DCs subsets in the pathogenesis of SSc, as well as to the novel developments on DCs in in-vivo models of SSc and the potential use of DCs and their mediators as therapeutic targets.

Serum miRNAs as potential biomarkers for the bronchiolitis obliterans syndrome after lung transplantation.

Lung transplantation (LTx) is the last treatment for patients suffering from end-stage lung diseases. Survival post-LTx is hampered by the development of the bronchiolitis obliterans syndrome (BOS) and diagnosis is often late. Given the urgent clinical need to recognize BOS patients at an early stage, we analyzed circulating miRNAs to identify possible stratification markers for BOS development post-transplantation. Therefore, pro-fibrotic (miR-21, miR-155), anti-fibrotic (miR-29a) and fibrosis-unrelated (miR-103, miR-191) miRNAs were analyzed in serum of end-stage lung disease patients and during LTx follow-up. Significant elevated levels of serum miRNAs were observed for all investigated miRNAs in both chronic obstructive pulmonary disease and interstitial lung disease patients compared to healthy controls. The same miRNAs were also significantly increased in the serum of BOS+ vs. BOS- patients. Most importantly, miR-21, miR-29a, miR-103, and miR-191 levels were significantly higher in BOS+ patients prior to clinical BOS diagnosis. We demonstrated that a selected group of miRNAs investigated is elevated in end-stage lung disease and BOS+ patients, prior to clinical BOS diagnosis. Even if further research is expedient on the prognostic value of circulating miRNAs in BOS and lung conditions in general, these results strongly suggest that circulating miRNAs could be used as potential biomarkers for BOS development.

Patients with gout have short telomeres compared with healthy participants: association of telomere length with flare frequency and cardiovascular disease in gout.

AIM AND BACKGROUND: Chronic inflammation associates with increased senescence, which is a strong predictor for cardiovascular disease. We hypothesised that inflammation accelerates senescence and thereby enhances the risk of cardiovascular disease in gout. METHODS: We assessed replicative senescence by quantifying telomere length (TL) in a discovery cohort of 145 Dutch patients with gout and 273 healthy individuals and validated our results in 474 patients with gout and 293 healthy participants from New Zealand. Subsequently, we investigated the effect of cardiovascular disease on TL of all participants. Also, we measured TL of CD4+ and CD8+ T lymphocytes, B lymphocytes, monocytes, natural killer cells and plasmacytoid dendritic cells. Additionally, we assessed the potential temporal difference in TL and telomerase activity. RESULTS: TL in PBMCs of healthy donors decreased over time, reflecting normal ageing. Patients with gout demonstrated shorter telomeres (p=0.001, R2=0.01873). In fact, the extent of telomere erosion in patients with gout was higher at any age compared with healthy counterparts at any age (p<0.0001, R2=0.02847). Patients with gout with cardiovascular disease had the shortest telomeres and TL was an independent risk factor for cardiovascular disease in patients with gout (p=0.001). TL was inversely associated with the number of gouty flares (p=0.005). CONCLUSIONS: Patients with gout have shorter telomeres than healthy participants, reflecting increased cellular senescence. Telomere shortening was associated with the number of flares and with cardiovascular disease in people with gout.

An Ocular Protein Triad Can Classify Four Complex Retinal Diseases.

Retinal diseases generally are vision-threatening conditions that warrant appropriate clinical decision-making which currently solely dependents upon extensive clinical screening by specialized ophthalmologists. In the era where molecular assessment has improved dramatically, we aimed at the identification of biomarkers in 175 ocular fluids to classify four archetypical ocular conditions affecting the retina (age-related macular degeneration, idiopathic non-infectious uveitis, primary vitreoretinal lymphoma, and rhegmatogenous retinal detachment) with one single test. Unsupervised clustering of ocular proteins revealed a classification strikingly similar to the clinical phenotypes of each disease group studied. We developed and independently validated a parsimonious model based merely on three proteins; interleukin (IL)-10, IL-21, and angiotensin converting enzyme (ACE) that could correctly classify patients with an overall accuracy, sensitivity and specificity of respectively, 86.7%, 79.4% and 92.5%. Here, we provide proof-of-concept for molecular profiling as a diagnostic aid for ophthalmologists in the care for patients with retinal conditions.

Functionally active NKG2A-expressing natural killer cells are elevated in rheumatoid arthritis patients compared to psoriatic arthritis patients and healthy donors.

OBJECTIVES: Natural killer cell receptors (NKR) have been implicated in rheumatoid (RA) and psoriatic arthritis (PsA) pathogenesis. To gain more insight into their role, we characterised NKR (co-)expression patterns on NK and T cells and NK cell function in RA and PsA. METHODS: The frequency of NK and T cells expressing killer like immunoglobulin (KIR) and NKG2 receptors and natural cytotoxicity receptors was assessed by 10-colour flow cytometry in peripheral blood of 23 RA, 12 PsA patients and 18 healthy donors (HD). NK cell cytotoxicity and IFN-gamma production was assessed in 8 RA patients and 8 HD. RESULTS: In RA but not PsA, the frequency of NK cells (median; range) expressing NKG2A (42%; 14-81%) was elevated compared to HD (23%; 9-58%). NKG2A⁺ NK cells predominantly lack KIR, but display normal cytotoxicity and IFN-γ production. In contrast, RA patients with normal NKG2A⁺ NK cell frequency have less functional NK cells compared to HD. T cells expressing Fc-gamma receptor CD16 were elevated in RA (median 0.75%) versus HD (0.3%). Furthermore, T cells expressing the KIRs CD158ah in both RA (0.7%) and PsA (0.3%), and CD158e1e2 in RA (1.5%) were elevated compared to HD (0.2% and 0.4%, respectively). In RA, CD4⁺ T cells expressing the KIRs CD158ah, CD158b1b2j and CD158e1e2 were low (<2%) but significantly elevated compared to HD. CONCLUSIONS: This study demonstrates the presence of an elevated, functionally active NKG2A⁺ KIR- NK cell population in RA. Together with an elevated frequency of NKR-expressing T cells, these changes may reflect differential pathogenetic involvement.

Proteomic analysis of plasma identifies the Toll-like receptor agonists S100A8/A9 as a novel possible marker for systemic sclerosis phenotype.

BACKGROUND: Systemic sclerosis (SSc) is an autoimmune disease characterised by fibrosis of the skin and the internal organs. Except for anticentromere, antitopoisomerase I and antipolymerase III antibodies, there are no reliable circulating markers predicting susceptibility and internal organ complications. This study has exploited a proteome-wide profiling method with the aim to identify new markers to identify SSc phenotype. METHOD: 40 SSc patients were included for proteomic identification. Patients were stratified as having diffuse cutaneous SSc (dcSSc) (n=19) or limited cutaneous SSc (lcSSc) (n=21) according to the extent of skin involvement. As controls 19 healthy donors were included. Blood was drawn and plasma was stored before analysing with the SELDI-TOF-MS. For replication in serum, the cohort was extended with 60 SSc patients. RESULTS: Proteomic analysis revealed a list of 25 masspeaks that were differentially expressed between SSc patients and healthy controls. One of the peaks was suggestive for S100A8, a masspeak we previously found in supernatant of plasmacytoid dendritic cells from SSc patients. Increased expression of S100A8/A9 in SSc patients was confirmed in replication cohort compared with controls. Intriguingly, S100A8/A9 was highest in patients with limited cutaneous SSc having lung fibrosis. CONCLUSIONS: S100A8/A9 was robustly found to be elevated in the circulation of SSc patients, suggesting its use as a biomarker for SSc lung disease and the need to further explore the role of TLR in SSc.

Evidence that deletion at FCGR3B is a risk factor for systemic sclerosis.

There is increasing evidence that gene copy number (CN) variation influences clinical phenotype. The low-affinity Fc receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment of polymorphonuclear neutrophils to sites of inflammation and their activation. Given the genetic overlap between systemic lupus erythematosus and systemic sclerosis (SSc) and the strong evidence for FCGR3B CN in the pathology of SLE, we hypothesised that FCGR3B gene dosage influences susceptibility to SSc. We obtained FCGR3B deletion status in 777 European Caucasian cases and 1000 controls. There was an inverse relationship between FCGR3B CN and disease susceptibility. CN of ≤ 1 was a significant risk factor for SSc (OR=1.55 (1.13-2.14), P=0.007) relative to CN ≥ 2. Although requiring replication, these results suggest that impaired immune complex clearance arising from FCGR3B deficiency contributes to the pathology of SSc, and FCGR3B CN variation is a common risk factor for systemic autoimmunity.

The autoimmune disease-associated IL2RA locus is involved in the clinical manifestations of systemic sclerosis.

Regulatory T cells (T(regs)) are crucial in the maintenance of the immune tolerance and seem to have an important role in systemic sclerosis (SSc). The interleukin 2 receptor α (IL2RA) is an important T(reg) marker, and polymorphisms of IL2RA gene are associated with a number of autoimmune diseases. Therefore, we aimed to investigate for the first time the association of the IL2RA locus in SSc. For this purpose, a total of 3023 SSc patients and 2735 matched healthy controls, from six European Caucasian cohorts, were genotyped for the IL2RA gene variants rs11594656, rs2104286 and rs12722495 using the TaqMan allelic discrimination technology. The overall meta-analysis reached statistical significance when the three polymorphisms were tested for association with SSc, the limited subtype (lcSSc) and anti-centromere auto-antibodies (ACAs). However, no significant P-values were obtained when the ACA-positive patients were removed from the SSc and lcSSc groups, suggesting that these associations rely on ACA positivity. The strongest association signal with ACA production was detected for rs2104286 (P(FDR)=2.07 × 10(-4), odds ratio=1.30 (1.14-1.47)). The associations of rs11594656 and rs12722495 were lost after conditioning to rs2104286, and allelic combination tests did not evidence a combined effect, indicating that rs2104286 best described the association between IL2RA and ACA presence in SSc.

Abatacept modulates proinflammatory macrophage responses upon cytokine-activated T cell and Toll-like receptor ligand stimulation.

OBJECTIVES: We investigated whether Abatacept might reduce proinflammatory cytokine production by macrophages upon contact with cytokine activated T cells and/or stimulation with TLR ligands. METHODS: Macrophages and cytokine stimulated T cells (Tck) were added together in the presence of Abatacept or a control Ig, with or without TLR ligands. The production of cytokines was determined by luminex. RESULTS: Abatacept reduced Tck-induced production of TNFa by macrophages. Tck and TLR ligands synergistically induced the production of proinflammatory cytokines by macrophages, especially IL-12p70. The production of IL-12p70 coincided with the production of IFNg, which were both reduced in the presence of Abatacept. CONCLUSIONS: Tck induce the production of TNFa by macrophages and facilitate the highly increased production of proinflammatory cytokines in the presence of TLR ligands. Abatacept was shown to potently suppress these pathways suggesting that its role may extend beyond antigen specific T cell mediated effector function.

A rare polymorphism in the gene for Toll-like receptor 2 is associated with systemic sclerosis phenotype and increases the production of inflammatory mediators.

OBJECTIVE: To investigate whether polymorphisms in Toll-like receptor (TLR) genes, previously reported to be associated with immune-mediated diseases, are involved in systemic sclerosis (SSc). METHODS: We genotyped 14 polymorphisms in the genes for TLRs 2, 4, 7, 8, and 9 in a discovery cohort comprising 452 SSc patients and 537 controls and a replication cohort consisting of 1,170 SSc patients and 925 controls. In addition, we analyzed 15-year followup data on 964 patients to assess the potential association of TLR variants with the development of disease complications. We analyzed the functional impact of the associated polymorphism on monocyte-derived dendritic cells. RESULTS: In the discovery cohort, we observed that a rare functional polymorphism in TLR2 (Pro631His) was associated with antitopoisomerase (antitopo) positivity (odds ratio 2.24 [95% confidence interval 1.24-4.04], P=0.003). This observation was validated in the replication cohort (odds ratio 2.73 [95% confidence interval 1.85-4.04], P=0.0001). In addition, in the replication cohort the TLR2 variant was associated with the diffuse subtype of the disease (P=0.02) and with the development of pulmonary arterial hypertension (PAH) (Cox proportional hazards ratio 5.61 [95% confidence interval 1.53-20.58], P=0.003 by log rank test). Functional analysis revealed that monocyte-derived dendritic cells carrying the Pro63His variant produced increased levels of inflammatory mediators (tumor necrosis factor α and interleukin-6) upon TLR-2-mediated stimulation (both P<0.0001). CONCLUSION: Among patients with SSc, the rare TLR2 Pro631His variant is robustly associated with antitopoisomerase positivity, the diffuse form of the disease, and the development of PAH. In addition, this variant influences TLR-2-mediated cell responses. Further research is needed to elucidate the precise role of TLR-2 in the pathogenesis of SSc.

Systematic validation of specific phenotypic markers for in vitro polarized human macrophages.

BACKGROUND: Polarization of macrophages by specific micro-environmental conditions impacts upon their function following subsequent activation. This study aimed to systematically validate robust phenotypic markers for in vitro polarized human macrophages in order to facilitate the study of macrophage subsets in vivo. METHODS: Human peripheral blood monocytes were polarized in vitro with IFN-γ, IL-4, or IL-10. Similar experiments were performed with TNF, IL-13, dexamethasone, M-CSF and GM-CSF as polarizing stimuli. Phenotypic markers were assessed by flow cytometry and qPCR. RESULTS: IFN-γ polarized macrophages (MΦ(IFN-γ)) specifically enhanced membrane expression of CD80 and CD64, IL-4 polarized macrophages (MΦ(IL-4)) mainly upregulated CD200R and CD206, and downregulated CD14 levels, and IL-10 polarized macrophages (MΦ(IL-10)) selectively induced CD163, CD16, and CD32. The expression profiles of the most specific markers were confirmed by qPCR, dose-response experiments, and the use of alternative polarizing factors for each macrophage subset (TNF, IL-13, and dexamethasone, respectively). GM-CSF polarized macrophages (MΦ(GM-CSF)) upregulated CD80 but not CD64 expression, showing a partial phenotypic similarity with MΦ(IFN-γ), and also upregulated the expression of the alternative activation marker CD206. M-CSF polarized macrophages (MΦ(M-CSF)) not only expressed increased levels of CD163 and CD16, resembling MΦ(IL-10,) but also displayed high levels of CD64. The phenotype of MΦ(M-CSF) could be further modulated by additional polarization with IFN-γ, IL-4, or IL-10, whereas MΦ(GM-CSF) showed less phenotypic plasticity. CONCLUSION: This study validated CD80 as the most robust phenotypic marker for human MΦ(IFN-γ), whereas CD200R was upregulated and CD14 was specifically downregulated on MΦ(IL-4). CD163 and CD16 were found to be specific markers for MΦ(IL-10). The GM-CSF/M-CSF differentiation model showed only a partial phenotypic similarity with the IFN-γ/IL-4/IL-10 induced polarization.

A system out of breath: how hypoxia possibly contributes to the pathogenesis of systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular alterations and immunological disturbances and fibrosis, the order of which remains to be fully determined. Clinically, patients show clear signs of hypoxia in skin and internal organs. The low oxygen tension is potentially caused by a yet to be indentified circuitry involving the three features that typify SSc. In addition, once present, the hypoxia creates a vicious circle of ongoing pathology. In this paper, we provide an overview of the evidence that points towards the mechanisms causing hypoxia in SSc. In addition, data that suggest how hypoxia itself may orchestrate worsening of symptoms is presented. Altogether, it is clear that hypoxia is an important hallmark in SSc patients. By providing an overview of the mechanisms at play and the possible therapeutic avenues that have emerged, we hope to stimulate researchers to provide novel clues into the conundrum in SSc patients.

An update on an immune system that goes awry in systemic sclerosis.

PURPOSE OF REVIEW: This review aims to provide an overview of the recent data that emerged, further substantiating the critical role of innate immunity in systemic sclerosis (SSc). RECENT FINDINGS: Driven by the evidence that newly identified SSc susceptibility genes are predominantly involved in immune regulation, we discuss the aberrant antigen presenting cell (APC) activation observed in the course of disease. In particular, we report the alternate activation of 'M1' and 'M2' macrophages reflecting different clinical phenotypes and the aberrant Toll-like receptor (TLR) response, whose effect on cytokine production is mostly evident in the early phases of disease; we especially highlight the increasing importance attributed to TLR3-mediated fibrosis. We next discuss the potential role for interferon (IFN) - producing plasmacytoid dendritic cells (pDCs) in triggering or perpetuating the inflammatory loop caused by TLR hyperactivation, possibly resulting in inflammasome-derived IL-1ß-mediated fibrosis and IL-17 producing T helper cells (Th17) skewing. SUMMARY: We propose to approach SSc as a multistep immune-mediated disease that is in need of a therapeutic strategy designed to interfere with one or more of these aberrant molecular pathways. Targeting of DCs could be such a target by which dampening the immune system could modify the course of SSc.