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Objective JIA is a chronic inflammatory disease of unknown origin. The regulation of inflammatory processes involves multiple cellular steps including mRNA transcription and translation. Different miRNAs control these processes tightly. We aimed to determine the roles of specific miRNAs within JIA pathogenesis. Methods We performed a global miRNA expression analysis in parallel in cells from the arthritic joint and peripheral blood of oligoarticular JIA patients and healthy controls. Quantitative RT-PCR analysis was used to verify expression of miRNA in T cells. Ex vivo experiments and flow cytometric analyses were used to analyse proliferation and redox metabolism. Results Global miRNA expression analysis demonstrated a different composition of miRNA expression at the site of inflammation compared with peripheral blood. Bioinformatic analysis of predicted miRNA target genes suggest a huge overrepresentation of genes involved in metabolic and oxidative stress pathways in the inflamed joint. Despite enhanced reactive oxygen species (ROS) levels within the local inflammatory milieu, JIA T cells are hyperproliferative and reveal an overexpression of miR-23a, which is an inhibitor of Peptidyl-prolyl isomerase F (PPIF), the regulator of mitochondrial ROS escape. Mitochondrial ROS escape is diminished in JIA T cells, resulting in their prolonged survival. Conclusion Our data suggest that miRNA-dependent mitochondrial ROS shuttling might be a mechanism that contributes to T cell regulation in JIA at the site of inflammation.

BACKGROUND. Deciphering the function of the many genes previously classified as uncharacterized open reading frame (ORF) would complete our understanding of a cell’s function and its pathophysiology. METHODS. Whole-exome sequencing, yeast 2-hybrid and transcriptome analyses, and molecular characterization were performed in this study to uncover the function of the C2orf69 gene. RESULTS. We identified loss-of-function mutations in the uncharacterized C2orf69 gene in 8 individuals with brain abnormalities involving hypomyelination and microcephaly, liver dysfunction, and recurrent autoinflammation. C2orf69 contains an N-terminal signal peptide that is required and sufficient for mitochondrial localization. Consistent with mitochondrial dysfunction, the patients showed signs of respiratory chain defects, and a CRISPR/Cas9-KO cell model of C2orf69 had similar respiratory chain defects. Patient-derived cells revealed alterations in immunological signaling pathways. Deposits of periodic acid–Schiff–positive (PAS-positive) material in tissues from affected individuals, together with decreased glycogen branching enzyme 1 (GBE1) activity, indicated an additional impact of C2orf69 on glycogen metabolism. CONCLUSIONS. Our study identifies C2orf69 as an important regulator of human mitochondrial function and suggests that this gene has additional influence on other metabolic pathways.

Neonatal sepsis is characterized by hyperinflammation causing enhanced morbidity and mortality compared to adults. This suggests differences in the response towards invading threats. Here we investigate activated cord blood macrophages (CBMΦ) in comparison to adult macrophages (PBMΦ), indicating incomplete interferon gamma (IFN-γ) and interleukin 10 (IL-10)-induced activation of CBMΦ. CBMΦ show reduced expression of phagocytosis receptors and cytokine expression in addition to altered energy metabolism. In particular, IFN-γ as well as IL-10-activated CBMΦ completely fail to increase glycolysis and furthermore show reduced activation of the mTOR pathway, which is important for survival in sepsis. MTOR inhibition by rapamycin equalizes cytokine production in CBMΦ and PBMΦ. Finally, incubation of PBMΦ with cord blood serum or S100A8/A9, which is highly expressed in neonates, suppresses mTOR activation, prevents glycolysis and the expression of an PBMΦ phenotype. Thus, a metabolic alteration is apparent in CBMΦ, which might be dependent on S100A8/A9 expression., Neonatal immune responses are known to differ to those of an adult immune response. Here Dreschers and colleagues, compare macrophage populations derived from cord blood or adult peripheral blood and show a metabolic impairment of glycolysis in macrophages derived from cord blood which may impair response to infective scenarios such as sepsis.

Frontiers in immunology 12, 1-7 (2021). doi:10.3389/fimmu.2021.633845 special issue: "Focusing on T-cells for Novel Treatments of Systemic Lupus Erythematosus", Published by Frontiers Media, Lausanne

BackgroundDeciphering the function of the many genes previously classified as uncharacterized “open reading frame” (orf) completes our understanding of cell function and its pathophysiology.MethodsWhole-exome sequencing, yeast 2-hybrid and transcriptome analyses together with molecular characterization are used here to uncover the function of the C2orf69 gene.ResultsWe identify loss-of-function mutations in the uncharacterized C2orf69 gene in eight individuals with brain abnormalities involving hypomyelination and microcephaly, liver dysfunction and recurrent autoinflammation. C2orf69 contains an N-terminal signal peptide that is required and sufficient for mitochondrial localization. Consistent with mitochondrial dysfunction, patients show signs of respiratory chain defect and a CRISPR-Cas9 knockout cell model of C2orf69 shows comparable respiratory chain defects. Patient-derived cells reveal alterations in immunological signaling pathways. Deposits of PAS-positive material in tissues from affected individuals together with decreased glycogen branching enzyme 1 (GBE1) activity indicate an additional impact of C2orf69 on glycogen metabolism.ConclusionOur study identifies C2orf69 as an important regulator of human mitochondrial function and suggests an additional influence on other metabolic pathways.Graphical Abstract

Signal transduction and targeted therapy 6(1), 392 (2021). doi:10.1038/s41392-021-00804-z, Published by Macmillan Publishers, part of Springer Nature, London

MΦ differentiate from circulating monocytes (Mo). The reduced ability of neonatal Mo to undergo apoptosis after E. coli infection (phagocytosis-induced cell death (PICD)) could contribute to sustained inflammatory processes. The objective of our study was to investigate whether immune metabolism in Mo can be modified to gain access to pro-apoptotic signaling. To this end, we supplemented Mo from neonates and from adults with the branched amino acid leucine. In neonatal Mo, we observed increased energy production via oxidative phosphorylation (Oxphos) after E. coli infection via Seahorse assay. Leucine did not change phagocytic properties. In neonatal Mo, we detected temporal activation of the AKT and mTOR pathways, accompanied with subsequent activation of downstream targets S6 Kinase (S6K) and S6. FACS analyses showed that once mTOR activation was terminated, the level of anti-apoptotic BCL-2 family proteins (BCL-2, BCL-XL) decreased. Release of cytochrome C and cleavage of caspase-3 indicated involvement of the intrinsic apoptotic pathway. Concomitantly, the PICD of neonatal Mo was initiated, as detected by hypodiploid DNA. This process was sensitive to rapamycin and metformin, suggesting a functional link between AKT, mTOR and the control of intrinsic apoptotic signaling. These features were unique to neonatal Mo and could not be observed in adult Mo. Supplementation with leucine therefore could be beneficial to reduce sustained inflammation in septic neonates.

Scientific reports 10(1), 624 (2020). doi:10.1038/s41598-019-56928-4, Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Background Allergic diseases and especially allergic asthma are widespread diseases with high prevalence in childhood, but also in adults. Acid sphingomyelinase (ASM) is a key regulator of the sphingolipid pathway. Previous studies defined the association of ASM with the pathogenesis of TH 1-directed lung diseases like cystic fibrosis and acute lung injury. Here, we define the role of ASM in TH 2-regulated allergic bronchial asthma. Methods To determine the role of Asm under baseline conditions, wild-type (WT) and Asm-/- mice were ventilated with a flexiVent setup and bronchial hyperresponsiveness was determined using acetylcholine. Flow cytometry and cytokine measurements in bronchoalveolar lavage fluid and lung tissue were followed by in vitro TH 2 differentiations with cells from WT and Asm-/- mice and blockade of Asm with amitriptyline. As proof of principle, we conducted an ovalbumin-induced model of asthma in WT- and Asm-/- mice. Results At baseline, Asm-/- mice showed better lung mechanics, but unaltered bronchial hyperresponsiveness. Higher numbers of Asm-/- T cells in bronchoalveolar lavage fluid released lower levels of IL-4 and IL-5, and these results were paralleled by decreased production of typical TH 2 cytokines in Asm-/- T lymphocytes in vitro. This phenotype could be imitated by incubation of T cells with amitriptyline. In the ovalbumin asthma model, Asm-/- animals were protected from high disease activity and showed better lung functions and lower levels of eosinophils and TH 2 cytokines. Conclusion Asm deficiency could induce higher numbers of TH 2 cells in the lung, but those cells release decreased TH 2 cytokine levels. Hereby, Asm-/- animals are protected from bronchial asthma, which possibly offers novel therapeutic strategies, for example, with ASM blockade.

European journal of immunology 50(4), 515-524 (2020). doi:10.1002/eji.201948285, Published by Wiley-VCH, Weinheim

Background The acute respiratory distress syndrome (ARDS) is a serious disease in critically ill patients that is characterized by pulmonary dysfunctions, hypoxemia and significant mortality. Patients with immunodeficiency (e.g. SCID with T and B cell deficiency) are particularly susceptible to the development of severe ARDS. However, the role of T cells on pulmonary dysfunctions in immune-competent patients with ARDS is only incompletely understood. Methods Wild-type (wt) and RAG2−/− mice (lymphocyte deficient) received intratracheal instillations of LPS (4 mg/kg) or saline. On day 1, 4 and 10 lung mechanics and bronchial hyperresponsiveness towards acetylcholine were measured with the flexiVent ventilation set-up. The bronchoalveolar lavage fluid (BALF) was examined for leukocytes (FACS analysis) and pro-inflammatory cytokines (ELISA). Results In wt mice, lung mechanics, body weight and body temperature deteriorated in the LPS-group during the early phase (up to d4); these alterations were accompanied by increased leukocyte numbers and inflammatory cytokine levels in the BALF. During the late phase (day 10), both lung mechanics and the cell/cytokine homeostasis recovered in LPS-treated wt mice. RAG2−/− mice experienced changes in body weight, lung mechanics, BAL neutrophil numbers, BAL inflammatory cytokines levels that were comparable to wt mice. Conclusion Following LPS instillation, lung mechanics deteriorate within the first 4 days and recover towards day 10. This response is not altered by the lack of T lymphocytes suggesting that T cells play only a minor role for the initiation, propagation or recovery of LPS-induced lung dysfunctions or function of T lymphocytes can be compensated by other immune cells, such as alveolar macrophages. Electronic supplementary material The online version of this article (10.1186/s12890-018-0741-2) contains supplementary material, which is available to authorized users.

Background/Aims: IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis and still constitutes one of the most important causes of end-stage renal disease. Abnormal T cell responses may play a role in IgAN pathogenesis. Co-stimulatory molecules such as cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) are important for naive T cells to initiate and terminate immune responses. Single nucleotide polymorphisms (SNPs) in the CTLA4 gene locus are associated with several autoimmune diseases. Methods: We aimed to investigate the occurrence of the SNPs -318C/T, +49A/G and CT60 G/A within the CTLA4 locus in healthy blood donors (n=455) and IgAN patients (n=252) recruited from the recently published STOP-IgAN trial. The presence of these SNPs was then associated with baseline proteinuria in IgAN patients. Results: We observed a significantly increased frequency of the CTLA4 -318C/T genotype in IgAN patients as compared to controls (CC vs. CT+TT: OR 1.65, 95%-CI 1.03-2.65, p=0.035). No significant associations, neither with the +49A/G nor for the CT60 G/A SNP, were detected. However, when we stratified for proteinuria at time of inclusion into the STOP-IgAN trial (1 g/day), we observed significant differences in the frequencies of the CT60 G/A genotype, i.e. a significantly increased risk for higher proteinuria in patients carrying the G allele (OR 2.81, 95%-CI 1.03-7.64, p=0.042). Conclusion: The CTLA4 -318/C/T SNP was associated with an increased risk to develop IgAN, while the CT60 G/A genotype significantly associated with the risk for higher proteinuria suggesting a possible role for CTLA-4 in IgAN.

Systemic lupus erythematosus (SLE) is an autoimmune disease and lupus nephritis is a major risk factor for morbidity and mortality. Notch-3 signaling induced by membrane-bound or soluble ligands such as YB-1 constitutes an evolutionarily conserved pathway that determines major decisions in cell fate. Mass spectrometry of extracellular YB-1 in sera from patients with SLE and lupus-prone mice revealed specific post-translational guanidinylation of two lysine residues within the highly conserved cold-shock domain of YB-1 (YB-1-G). These modifications highly correlated with SLE disease activity, especially in patients with lupus nephritis and resulted in enhanced activation of Notch-3 signaling in T lymphocytes. The importance of YB-1:Notch-3 interaction in T cells was further evidenced by increased interleukin (Il)10 expression following YB-1-G stimulation and detection of both, YB-1-G and Notch-3, in kidneys of MRL.lpr mice by mass spectrometry imaging. Notch-3 expression and activation was significantly up-regulated in kidneys of 20-week-old MRL.lpr mice. Notably, lupus-prone mice with constitutional Notch-3 depletion (B6.Faslpr/lprNotch3−/−) exhibited an aggravated lupus phenotype with significantly increased mortality, enlarged lymphoid organs and aggravated nephritis. Additionally, these mice displayed fewer regulatory T cells and reduced amounts of anti-inflammatory IL-10. Thus, our results indicate that the YB-1:Notch-3 axis exerts protective effects in SLE and that Notch-3 deficiency exacerbates the SLE phenotype.

Gut : an international journal of gastroenterology and hepatology 66(5), 908-919 (2016). doi:10.1136/gutjnl-2015-311119, Published by BMJ Publishing Group, London

Frontiers in immunology 9, 2499 (2018). doi:10.3389/fimmu.2018.02499, Published by Frontiers Media, Lausanne

Background Inflammatory effector T cells trigger inflammation despite increased numbers of Treg cells in the synovial joint of patients suffering from juvenile idiopathic arthritis (JIA). The cAMP response element (CREM)α is known to play a major role in regulation of T cells in SLE, colitis, and EAE. However, its role in regulation of effector T cells within the inflammatory joint is unknown. Methods CREM expression was analyzed in synovial fluid cells from oligoarticular JIA patients by flow cytometry. Peripheral blood mononuclear cells were incubated with synovial fluid and analyzed in the presence and absence of CREM using siRNA experiments for T cell phenotypes. To validate the role of CREM in vivo, ovalbumin-induced T cell dependent arthritis experiments were performed. Results CREM is highly expressed in synovial fluid T cells and its expression can be induced by treating healthy control PBMCs with synovial fluid. Specifically, CREM is more abundant in CD161+ subsets, than CD161− subsets, of T cells and contributes to cytokine expression by these cells. Finally, development of ovalbumin-induced experimental arthritis is ameliorated in mice with adoptively transferred CREM−/− T cells. Conclusion In conclusion, our study reveals that beyond its role in SLE T cells CREM also drives an inflammatory phenotype of T cells in JIA.

Accumulating evidence suggests that oxidative stress plays a major role in the pathogenesis of multiple sclerosis (MS). Reactive oxygen species (ROS), which if produced in excess lead to oxidative stress, have been implicated as mediators of demyelination and axonal damage in both MS and its animal models. One of the most studied cell populations in the context of ROS-mediated tissue damage in MS are macrophages and their CNS companion, microglia cells. However, and this aspect is less well appreciated, the extracellular and intracellular redox milieu is integral to many processes underlying T cell activation, proliferation and apoptosis. In this review article we discuss how oxidative stress affects central as well as peripheral aspects of MS and how manipulation of ROS pathways can potentially affect the course of the disease. It is our strong belief that the well-directed shaping of ROS pathways has the potential to ameliorate disease progression in MS.

Molecular factors driving immune-mediated inflammation in the liver are incompletely understood. The transcription factor, cyclic adenosine monophosphate-responsive element modulator alpha (CREMα) can endorse differentiation of T lymphocytes toward T-helper (Th)17 cells, thereby promoting autoimmunity in systemic lupus erythematosus or lung inflammation. To investigate the role of CREMα in liver disease, we subjected transgenic (Tg) mice overexpressing CREMα under control of the CD2 promoter (cremtg mice), which restrains expression mainly to lymphocytes (T, natural killer [NK], and NKT cells), to acute and chronic liver injury models. Already in steady state, Tg CREMα overexpression broadly reduced hepatic immune cell numbers by decreasing their viability, but did not affect immune cell migration or the fibrogenic response to chronic liver injury. Strikingly, cremtg mice developed more severe immune-mediated hepatitis with a higher mortality rate, compared to wild-type (wt) mice, upon concanavalin A (ConA) administration. Unlike in T cells from spleen, CREMα overexpression did not induce a predominant Th17 response in intrahepatic T cells, given that hepatic cremtg CD4+ T cells expressed less interleukin (IL)-17 than wt T cells. Reconstitution of Rag1−/− mice with Crem−/− T cells did not ameliorate ConA hepatitis. Overexpression of CREMα did not influence NK and NKT-cell effector functions either. Interestingly, a subset of monocytic myeloid-derived suppressor cells (MDSCs) also expressed CD2 and CREMα. Cremtg MDSCs isolated from liver expressed reduced inducible nitric oxide synthase and arginase 1 and displayed a reduced T-cell suppressive activity. The adoptive transfer of wt MDSCs was capable of reducing the fulminant immune-mediated liver damage in cremtg mice to wt level. Conclusion: These results suggest compartmental differences of T cell activation pathways between liver and other organs in autoimmunity and define a functional role of CREMα in hepatic monocytic MDSCs for the pathogenesis of immune-mediated liver disease. (Hepatology 2015;61:990–1002)

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with chemokine-like functions that plays a pivotal role in the pathogenesis of inflammatory diseases by promoting leukocyte recruitment. We showed that MIF promotes the atherogenic recruitment of monocytes and T cells through its receptors CXCR2 and CXCR4. Effects of MIF on B cell recruitment have not been addressed. In this study, we tested the involvement of MIF in B cell chemotaxis and studied the underlying mechanism. We show that MIF promotes primary murine B cell chemotaxis in a dose-dependent manner, comparable to the B cell chemokines CXCL13 and CXCL12. Splenic B cells express CXCR4 and the receptor CD74 but not CXCR2. Inhibition of CXCR4 or CD74 or a genetic deficiency of Cd74 in primary B cells fully abrogated MIF-mediated B cell migration, implying cooperative involvement of both receptors. MIF stimulation of B cells resulted in a rapid increase in intracellular Ca2+ mobilization and F-actin polymerization. Intriguingly, the tyrosine kinase ZAP-70 was activated upon MIF and CXCL12 treatment in a CXCR4- and CD74-dependent manner. Pharmacological inhibition of ZAP-70 resulted in abrogation of primary B cell migration. Functional involvement of ZAP-70 was confirmed by small interfering RNA–mediated knockdown in Ramos B cell migration. Finally, primary B cells from ZAP-70 gene–deficient mice exhibited ablated transmigration in response to MIF or CXCL12. We conclude that MIF promotes the migration of B cells through a ZAP-70–dependent pathway mediated by cooperative engagement of CXCR4 and CD74. The data also suggest that MIF may contribute to B cell recruitment in vivo (e.g., in B cell–related immune disorders).

Objective Interleukin-6 (IL-6) signaling plays an important proinflammatory role, but this role is restricted by regulatory mechanisms that, for example, reduce the cell surface availability of the signal-transducing chain of the IL-6 receptor, gp130. The aim of this study was to determine whether the inflammatory environment in arthritic joints has an impact on monocytic gp130 surface expression and the extent to which regulatory processes in the synovial fluid (SF) can be reproduced in an in vitro model. Methods Flow cytometry and live cell imaging were used to measure the cell surface expression and internalization of gp130. STAT-3 phosphorylation was monitored by flow cytometry and Western blotting. Results In patients with juvenile idiopathic arthritis (JIA), levels of cell surface gp130 expression in SF monocytes were reduced compared to those in peripheral blood (PB) monocytes. These reduced levels were reproduced when PB monocytes from healthy donors were stimulated with SF, and this reduction was dependent on p38 MAPK. The induction of p38 by IL-1β in PB monocytes interfered with IL-6 signaling due to the reduced cell surface expression of gp130. Conclusion These results suggest that p38-mediated proinflammatory stimuli induce the down-regulation of gp130 on monocytes and thus restrict gp130-mediated signal transduction. This regulatory mechanism could be of relevance to processes in the inflamed joints of patients with JIA.

Frontiers in immunology 7, 618 (2016). doi:10.3389/fimmu.2016.00618, Published by Frontiers Media, Lausanne

Transcription factor cAMP response element modulator (CREM)α contributes to various cellular and molecular abnormalities in T cells, including increased IL-17 and decreased IL-2 expression. For development of acute lung injury (ALI), the invasion and regulation of immune cells are highly important, but the role of T cells remains unclear. In this study, we show that CREMα is upregulated in LPS-induced ALI. During the early phase of ALI (day 1), T cell–specific CREMα overexpression enhances the numbers of T cells and expression of TNF-α in bronchoalveolar lavage fluid and deteriorates lung functions. On day 3 of ALI, CREMα transgenic mice present a stronger inflammatory response with higher levels of TNF-α, IL-6, and IL-17 correlating with increased numbers of T cells and neutrophils in bronchoalveolar lavage fluid, whereas expression of Foxp3 and IL-2 and numbers of regulatory T cells are decreased. These changes result in restricted lung function in CREMα transgenic mice. Finally, an adoptive transfer of CREM−/− CD4+ T cells, but not of wild-type T cells into RAG-1−/− mice results in ameliorated disease levels. Thus, levels of CREM in T cells determine the outcome of ALI, and CREMα transgenic animals represent a model in which proinflammatory T cells aggravate ALI in different phases of the disease. Given the fact that patients with autoimmune diseases like systemic lupus erythematosus show higher levels of CREMα and an increased susceptibility toward infectious complications, our finding is of potential clinical significance and may enable new therapeutic strategies.

Brain-intrinsic degenerative cascades have been proposed to be an initial factor driving lesion formation in multiple sclerosis (MS). Here, we identify neurodegeneration as a potent trigger for peripheral immune cell recruitment into the mouse forebrain. Female C57BL/6 mice were fed cuprizone for 3 weeks, followed by a period of 2 weeks on normal chow to induce the formation of lesion foci in the forebrain. Subsequent immunization with myelin oligodendrocyte glycoprotein 35–55 peptide, which induces myelin autoreactive T cells in the periphery, resulted in massive immune cell recruitment into the affected forebrain. Additional adoptive transfer experiments together with flow cytometry analysis underline the importance of brain-derived signals for immune cell recruitment. This study clearly illustrates the significance of brain-intrinsic degenerative cascades for immune cell recruitment and MS lesion formation. Additional studies have to address the signaling cascades and mechanistic processes that form the top-down communication between the affected brain area, neurovascular unit, and peripheral immune cells.SIGNIFICANCE STATEMENTWe identify neurodegeneration as a potent trigger for peripheral immune cell recruitment into the forebrain. Thus, immune cell recruitment might be a second step during the formation of new inflammatory lesions in multiple sclerosis. A better understanding of factors regulating neurodegeneration-induced immune cell recruitment will pave the way for the development of novel therapeutic treatment strategies.

Background: IL-12p40 plays an important role in the activation of the T-cell lines like Th17 and Th1-cells. Theses cells are crucial in the pathogenesis of juvenile idiopathic arthritis. A polymorphism in its promoter region and the genotype IL12p40 pro1.1 leads to a higher production of IL-12p40. We studied whether there is a difference in the distribution of the genotype in patients with JIA and the healthy population. Methods: In 883 patients and 321 healthy controls the IL-12p40 promoter genotype was identified by ARMS-PCR. Results: There is no association of IL-12p40 pro polymorphism neither in patients with JIA compared to controls nor in subtypes of JIA compared to oligoarthritis. We found a non-significant tendency of a higher prevalence of the genotype pro1.1 in systemic arthritis (32.4 %) and in rheumatoid factor negative polyarthritis (30.5 %) and a lower pro1.1 genotype in persistent oligoarthritis (20.7 %) and in enthesitis-related arthritis (17 %). Likelihood of the occurrence of genotype IL12-p40 pro1.1 in patients with systemic arthritis (OR 1.722, CI 95 % 1.344-2.615, p 0.0129) and RF-negative polyarthritis (OR 1.576, CI 95 % 1.046-2.376, p 0.0367) compared to persistent oligoarthritis was significantly higher. This was also true for comparison of their homozygous genotypes IL-12p40 pro 1.1 and 2.2 in systemic arthritis (OR 1.779, CI 95 % 1.045-3.029, p 0.0338). However, in Bonferroni correction for multiple hypothesis this was not significant. Conclusion: A tendency of a higher prevalence of the genotype IL-12p40 pro1.1 in systemic arthritis and in rheumatoid factor negative polyarthritis was observed but not significant. Further investigations should be done to clarify the role IL-12p40 in the different subtypes of JIA.

OncoTarget 6(36), 38538-38551 (2015). doi:10.18632/oncotarget.6041, Published by Impact Journals LLC, [S.l.]

Summary The recruitment of immune cells to sites of tissue inflammation is orchestrated by chemokine/chemokine receptor networks. Among these, the CXCL13/CXCR5 axis is thought to be involved critically in systemic lupus erythematosus (SLE) and lupus nephritis pathogenesis. Beyond B cell abnormalities, another hallmark of SLE disease is the occurrence of aberrant T cell responses. In particular, double-negative (DN) T cells are expanded in the peripheral blood of patients with SLE and in lupus-prone mice. DN T cells induce immunoglobulin production, secrete proinflammatory cytokines and infiltrate inflamed tissue, including kidneys. We aimed to investigate how CXCR5 deficiency changes immune cell trafficking in murine lupus. We therefore crossed CXCR5–/– mice with B6/lpr mice, a well-established murine lupus model. B cell numbers and B cellular immune responses were diminished in CXCR5-deficient B6/lpr mice. In addition, we observed reduced accumulation of DN T cells in spleen and lymph nodes, paralleled by reduced splenomegaly and lymphadenopathy. In-vivo migration assays revealed reduced migration of CXCR5-deficient DN T cells into lymph nodes, and ex-vivo-activated CXCR5-deficient DN T cells failed to infiltrate kidneys of recipients. Moreover, DN T cells and B cells of CXCR5-deficient B6/lpr mice failed to migrate towards CXCL13 in vitro. We propose that CXCR5 is involved critically in B cell trafficking and germinal cell (GC) formation in murine lupus and in guiding pathogenic DN T cells into lymphoid organs and kidneys, and we therefore describe new pathomechanisms for the CXCL13/CXCR5 axis in SLE.

Summary Systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), are often characterized by a failure of self-tolerance and result in an uncontrolled activation of B cells and effector T cells. Interleukin (IL)-2 critically maintains homeostasis of regulatory T cells (Treg) and effector T cells in the periphery. Previously, we identified the cAMP-responsive element modulator α (CREMα) as a major factor responsible for decreased IL-2 production in T cells from SLE patients. Additionally, using a transgenic mouse that specifically over-expresses CREMα in T cells (CD2CREMαtg), we provided in-vivo evidence that CREMα indeed suppresses IL-2 production. To analyse the effects of CREMα in an autoimmune prone mouse model we introduced a Fas mutation in the CD2CREMαtg mice (FVB/Fas–/–CD2CREMαtg). Overexpression of CREMα strongly accelerated the lymphadenopathy and splenomegaly in the FVB/Fas–/– mice. This was accompanied by a massive expansion of double-negative (DN) T cells, enhanced numbers of interferon (IFN)-γ-producing T cells and reduced percentages of Tregs. Treatment of FVB/Fas–/–CD2CREMαtg mice with IL-2 restored the percentage of Tregs and reversed increased IFN-γ production, but did not affect the number of DNTs. Our data indicate that CREMα contributes to the failure of tolerance in SLE by favouring effector T cells and decreasing regulatory T cells, partially mediated by repression of IL-2 in vivo.

A broad spectrum of diseases is characterized by myelin abnormalities and/or oligodendrocyte pathology. In most, if not all, of these diseases, early activation of microglia occurs. Our knowledge regarding the factors triggering early microglia activation is, however, incomplete. In this study, we used the cuprizone model to investigate the temporal and causal relationship of oligodendrocyte apoptosis and early microglia activation. Genome-wide gene expression studies revealed the induction of distinct chemokines, among them Cxcl10, Ccl2, and Ccl3 in cuprizone-mediated oligodendrocyte apoptosis. Early microglia activation was unchanged in CCL2- and CCL3-deficient knockouts, but was significantly reduced in CXCL10-deficient mice, resulting in an amelioration of cuprizone toxicity at later time points. Subsequent in vitro experiments revealed that recombinant CXCL10 induced migration and a proinflammatory phenotype in cultured microglia, without affecting their phagocytic activity or proliferation. In situ hybridization analyses suggest that Cxcl10 mRNA is mainly expressed by astrocytes, but also oligodendrocytes, in short-term cuprizone-exposed mice. Our results show that CXCL10 actively participates in the initiation of microglial activation. These findings have implications for the role of CXCL10 as an important mediator during the initiation of neuroinflammatory processes associated with oligodendrocyte pathology.

In patients with juvenile idiopathic arthritis (JIA) high levels of IL-6 are present in the serum and synovial fluid (SF). IL-6 signaling plays an important pro-inflammatory role but is restricted by regulatory mechanisms such as reducing the cell surface availability of the signal-transducing chain of the IL-6 receptor (gp130).

Notch signaling constitutes an evolutionarily conserved pathway that transduces signals between neighboring cells and determines major decisions in cell proliferation, survival, and differentiation. Notch signaling has been shown to play a pivotal role during T cell lineage determination. T lymphocytes from patients with systemic lupus erythematosus (SLE) display a severely altered phenotype with several molecular and functional aberrations, including defective capacities to up-regulate Notch-1 receptor expression upon T cell receptor activation. Here, we demonstrate that basal Notch-1 expression is decreased in T cells from active SLE patients at the mRNA and protein levels in various T cell subpopulations. Notch-1 transcript numbers inversely correlate with disease activity in SLE patients. We provide evidence that both enhanced histone H3 methylation and CpG DNA methylation of the human Notch-1 promoter contribute to decreased Notch-1 expression in SLE T cells. Previous data from our group identified cAMP-responsive element modulator α (CREMα), which is up-regulated in SLE T cells, as a key regulator of epigenetic patterns and gene transcription, e.g. that of IL2 and IL17 genes. In this study, we observed increased CREMα binding to the Notch-1 promoter, which eventually resulted in significantly reduced Notch-1 promoter activity and gene transcription. Notably, decreased Notch-1 levels were associated with elevated IL-17A levels. Our data suggest a role for Notch-1 in SLE immunopathogenesis, and for the first time, we present molecular mechanisms that mediate dysregulated Notch-1 expression in SLE T cells.

Journal of biomedicine & biotechnology : JBB 2011, 432595 (2011). doi:10.1155/2011/432595, Published by Hindawi, Akron, Ohio

MIF is a chemokine-like inflammatory mediator that triggers leukocyte recruitment by binding to CXCR2 and CXCR4. MIF also interacts with CD74/invariant chain, a single-pass membrane-receptor. We identified complexes between CD74 and CXCR2 with a role in leukocyte recruitment. It is unknown whether CD74 also binds to CXCR4. We demonstrate that CD74/CXCR4 complexes formed when CD74 was expressed with CXCR4 in HEK293 cells. Expression of CD74-variants lacking an ER-retention signal showed CD74/CXCR4 complexes at the cell surface. Importantly, endogenous CD74/CXCR4 complexes were isolated by co-immunoprecipitation from monocytes. Finally, MIF-stimulated CD74-dependent AKT activation was blocked by anti-CXCR4 and anti-CD74 antibodies and AMD3100, whereas CXCL12-stimulated AKT activation was not reduced by anti-CD74. Thus, CD74 forms functional complexes with CXCR4 that mediate MIF-specific signaling.Structured summaryMINT-7234512, MINT-7234528: CD74 (uniprotkb:P04233) physically interacts (MI:0915) with CXCR4 (uniprotkb:P61073) by anti tag coimmunoprecipitation (MI:0007)MINT-7234542: CD74 (uniprotkb:P04233) and CXCR4 (uniprotkb:P61073) physically interact (MI:0915) by anti bait coimmunoprecipitation (MI:0006)MINT-7234499: CXCR4 (uniprotkb:P61073) and CD74 (uniprotkb:P04233) colocalize (MI:0403) by fluorescence microscopy (MI:0416)

Patients with autoimmune diseases are highly susceptible towards infectious complications. In patients with SLE, infections are even one of the most common causes of morbidity, hospitalization and death. CREMα is a transcription factor, which is overexpressed in T cells from patients with systemic lupus erythematosus (SLE). Beyond this, CREMα is also upregulated in a murine model of LPS-induced acute lung injury (ALI).