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IL-17-producing CD8 + (Tc17) cells are enriched in active lesions of patients with multiple sclerosis (MS), suggesting a role in the pathogenesis of autoimmunity. Here we show that amelioration of MS by dimethyl fumarate (DMF), a mechanistically elusive drug, associates with suppression of Tc17 cells. DMF treatment results in reduced frequency of Tc17, contrary to Th17 cells, and in a decreased ratio of the regulators RORC -to- TBX21 , along with a shift towards cytotoxic T lymphocyte gene expression signature in CD8 + T cells from MS patients. Mechanistically, DMF potentiates the PI3K-AKT-FOXO1-T-BET pathway, thereby limiting IL-17 and RORγt expression as well as STAT5-signaling in a glutathione-dependent manner. This results in chromatin remodeling at the Il17 locus. Consequently, T-BET-deficiency in mice or inhibition of PI3K-AKT, STAT5 or reactive oxygen species prevents DMF-mediated Tc17 suppression. Overall, our data disclose a DMF-AKT-T-BET driven immune modulation and suggest putative therapy targets in MS and beyond. Dimethyl fumarate (DMF) is a therapy for multiple sclerosis (MS) with undetermined mechanism of action. Here the authors find that clinical response to DMF associates with decrease in IL-17-producing CD8 +  T cells (Tc17), delineate molecular pathways involved, and show that DMF suppresses Tc17 pathogenicity in a mouse model of MS.

Key Points Transcription factors of the interferon (IFN)-regulatory factor (IRF) family were originally identified by their capacity to mediate the effects of type I IFNs. Ten IRF-family members have now been defined on the basis of sequence homology and the ability to bind a common DNA motif in various gene promoters. In the past seven years, many IRFs have been found to be involved in T helper (T H )-cell differentiation, a consequence of their capacity to influence the function of accessory cells. This influence leads to alterations in gene products that are important for differentiation into T H 1 or T H 2 cells, such as interleukin-12 (IL-12), IL-18, IL-23, type I IFNs and nitric oxide. Recent evidence has shown an additional T-cell-intrinsic role for IRF1, -2 and -4 during T H -cell differentiation. This role can be shown even when highly purified naive T H cells are studied in the absence of any accessory cell. IRF1 and IRF2 interact with each other and bind elements in the IL-4 promoter, suppressing its activity. Evidence is accumulating that IRF1 is a multifunctional transcription factor that influences several different cell types and genes to modify the differentiation of T H cells into either T H 1 or T H 2 cells. Importantly, all of the activities of IRF1 are directed towards a T H 1 response, making IRF1 an attractive target for therapeutic intervention in diseases with increased or deficient T H 1-cell responses, such as multiple sclerosis or asthma. IRF4 mainly drives T H 2-cell development but might also influence T H 1-cell development. IRF4 acts intrinsically on T H cells, functions upstream of GATA-binding protein 3 (GATA3) and might interact with signal transducer and activator of transcription 6 (STAT6), B-cell lymphoma 6 (BCL-6) and/or nuclear factor of activated T cells 1 (NFAT1) and/or NFAT2. Members of the interferon-regulatory factor family of transcription factors have long been known to be intracellular mediators of the effects of interferons. In recent years, interferon-regulatory factors have also been shown to have an essential role in the differentiation of T helper cells, both by modulating the functions of antigen-presenting cells and by having direct effects on the T helper cells themselves. Depending on the interferon-regulatory factor involved, the differentiation of T helper cells to either T helper 1 cells or T helper 2 cells can be influenced. In this article, we provide an overview of this relatively new and still underappreciated role of interferon-regulatory factors.

Differentiation of murine T-helper (Th) 17 cells is induced by antigenic stimulation and the sequential action of the cytokines IL-6, IL-21, and IL-23, along with TGFβ. Current dogma proposes that IL-6 induces IL-21, which, in a STAT3-dependent manner, amplifies its own transcription, contributes to IL-17 production, and, moreover, promotes the expression of the IL-23 receptor. This, in turn, prepares cells for IL-23-mediated stabilization of the Th17 phenotype. Here we demonstrate that these effects of IL-21 on Th17 differentiation are completely dependent on IFN regulatory factor 4 (IRF4). After culturing in the presence of IL-21 plus TGFβ, IRF4-deficient (Irf4⁻/⁻) Th cells showed a profound intrinsic defect in IL-17 production and in the autocrine IL-21 loop. Likewise, the levels of IL-23 receptor and the lineage-specific orphan nuclear receptors RORα and RORγt were diminished, whereas the T regulatory (Treg) transcription factor forkhead box P3 (Foxp3) was strongly up-regulated, consistent with the reciprocal relationship between Th17 and Treg development. Despite this loss of IL-21 functions, IL-21-induced STAT3 activation was unimpaired and induced normal Socs3 expression. Forced expression of Foxp3 in WT cells inhibited IL-21-mediated IL-17 production, suggesting that the increase in Foxp3 contributes to the Irf4⁻/⁻ phenotype. Additionally, the low levels of RORα and RORγt are also partially responsible, because simultaneous overexpression of both proteins restored IL-17 production in Irf4⁻/⁻ cells to some extent. These data highlight IRF4 as a decisive factor during the IL-21-mediated steps of Th17 development by influencing the balance of Foxp3, RORα, and RORγt.

Interferon-regulatory factor 4 (IRF4) is essential for the development of T helper type 2 cells. Here we show that IRF4 is also critical for the generation of interleukin 17–producing T helper cells (T H -17 cells), which are associated with experimental autoimmune encephalomyelitis. IRF4-deficient ( Irf4 −/− ) mice did not develop experimental autoimmune encephalomyelitis, and T helper cells from such mice failed to differentiate into T H -17 cells. Transfer of wild-type T helper cells into Irf4 −/− mice rendered the mice susceptible to experimental autoimmune encephalomyelitis. Irf4 −/− T helper cells had less expression of RORγt and more expression of Foxp3, transcription factors important for the differentiation of T H -17 and regulatory T cells, respectively. Altered regulation of both transcription factors contributed to the phenotype of Irf4 −/− T helper cells. Our data position IRF4 at the center of T helper cell development, influencing not only T helper type 2 but also T H -17 differentiation.

Follicular T-helper (TFH) cells cooperate with GL7+CD95+ germinal center (GC) B cells to induce antibody maturation. Herein, we identify the transcription factor IRF4 as a T-cell intrinsic precondition for TFH cell differentiation and GC formation. After immunization with protein or infection with the protozoon Leishmania major, draining lymph nodes (LNs) of IFN-regulatory factor-4 (Irf4–/–) mice lacked GCs and GC B cells despite developing normal initial hyperplasia. GCs were also absent in Peyer’s patches of naive Irf4–/– mice. Accordingly, CD4+ T cells within the LNs and Peyer’s patches failed to express the TFH key transcription factor B-cell lymphoma-6 and other TFH-related molecules. During chronic leishmaniasis, the draining Irf4–/– LNs disappeared because of massive cell death. Adoptive transfer of WT CD4+ T cells or few L. major primed WT TFH cells reconstituted GC formation, GC B-cell differentiation, and LN cell survival. In support of a T-cell intrinsic IRF4 activity, Irf4–/– TFH cell differentiation was not rescued by close neighborhood to transferred WT TFH cells. Together with its known B lineage-specific roles during plasma cell maturation and class switch, our study places IRF4 in the center of antibody production toward T-cell–dependent antigens.

Diagnostic tests for visceral leishmaniasis that are based on antigens of a single Leishmania strain can have low diagnostic performance in regions where heterologous parasites predominate. The aim of this study was to investigate and compare the performance of five serological tests, based on different Leishmania antigens, in three endemic countries for visceral leishmaniasis. A total number of 231 sera of symptomatic and asymptomatic cases and controls from three endemic regions of visceral leishmaniasis in East Sudan, North India and South France were evaluated by following serological tests: rKLO8- and rK39 ELISA, DAT (ITMA-DAT) and two rapid tests of rK39 (IT LEISH) and rKE16 (Signal-KA). Overall, rKLO8- and rK39 ELISA were most sensitive in immunocompetent patients from all endemic regions (96-100%) and the sensitivity was reduced to 81.8% in HIV co-infected patients from France. Sera of patients from India demonstrated significantly higher antibody responses to rKLO8 and rK39 compared with sera from Sudan (p<0.0001) and France (p<0.0037). Further, some Indian and Sudanese patients reacted better with rKLO8 than rK39. Sensitivity of DAT (ITMA-DAT) was high in Sudan (94%) and India (92.3%) but low in France being 88.5% and 54.5% for VL and VL/HIV patients, respectively. In contrast, rapid tests displayed high sensitivity only in patients from India (96.2%) but not Sudan (64-88%) and France (73.1-88.5% and 63.6-81.8% in VL and VL/HIV patients, respectively). While the sensitivity varied, all tests showed high specificity in Sudan (96.7-100%) and India (96.6%).Heterogeneity of Leishmania parasites which is common in many endemic regions complicates the diagnosis of visceral leishmaniasis. Therefore, tests based on homologous Leishmania antigens are required for particular endemic regions to detect cases which are difficult to be diagnosed with currently available tests.

IntroductionAlthough there is increasing evidence for the successful use of local vancomycin applied by soaked compresses during ACL reconstruction, there are still little data on its microbiological and biomechanical effects. Furthermore, exact dosage of vancomycin with respect to tendon stability and microbiological effectivity is still unknown.Materials and methods63 porcine flexor digitorum profundus tendons were harvested under sterile conditions from fresh cadaver legs. After contamination with Staphylococcus epidermidis (S. epidermidis), tendons were wrapped into sterile compresses moistened with different concentrations of vancomycin for 10 or 20 min. Sterile sodium chloride was used for control. After treatment, tendons were rolled onto blood-agar plates to test for residual bacterial contamination and tested for maximum load and stiffness using a uniaxial testing device with cryo-clamps for tendon fixation. Agar plates were checked after 1 week of culture at 36 °C for signs of bacterial growth.ResultsWhen applying vancomycin for only 10 min, bacterial contamination was found in all dosage groups ranging from 28.6% contamination (n = 2 of 7 tendons) when using 10 mg/ml up to 85.7% (n = 6 of 7 tendons) when using 1 mg/ml. Applying vancomycin-soaked compresses for 20 min, bacterial contamination was still found in the groups using 1 mg/ml and 2.5 mg/ml (contamination rate 85.7 and 42.9% respectively). When using 5 mg/ml and 10 mg/ml, no bacterial contamination could be perceived after 7 days of culture. With regard to biomechanical properties, no differences were found regarding maximum load or Young’s modulus between groups.ConclusionsThis study showed no signs of biomechanical impairment of porcine flexor tendons after the use of vancomycin wraps with concentration ranging from 1 to 10 mg/ml for 10 or 20 min at a time zero testing. Contamination with S. epidermidis was cleansed in 100% of tendons when using at least 5 mg/ml of vancomycin for 20 min.

Here we compared SARS-CoV-2-specific antibody and T-cell responses between older adults (>80 years old, n  = 51) and a younger control group (20–53 years old, n  = 46) after receiving two doses of BNT162b2. We found that responses in older adults were generally lower, and we identified 10% low-/non-responders. After receiving a third vaccination with BNT162b2, 4 out of 5 low-/non-responders showed antibody and T-cell responses similar to those of responders after two vaccinations. A third vaccination with BNT162b2 against SARS-CoV-2 elicits antibody and T-cell responses in 4 out of 5 reported older adults who were previously low-/non-responders.

The T helper 9 (Th9) cell transcriptional network is formed by an equilibrium of signals induced by cytokines and antigen presentation. Here we show that, within this network, two interferon regulatory factors (IRF), IRF1 and IRF4, display opposing effects on Th9 differentiation. IRF4 dose-dependently promotes, whereas IRF1 inhibits, IL-9 production. Likewise, IRF1 inhibits IL-9 production by human Th9 cells. IRF1 counteracts IRF4-driven Il9 promoter activity, and IRF1 and IRF4 have opposing function on activating histone modifications, thus modulating RNA polymerase II recruitment. IRF1 occupancy correlates with decreased IRF4 abundance, suggesting an IRF1-IRF4-binding competition at the Il9 locus. Furthermore, IRF1 shapes Th9 cells with an interferon/Th1 gene signature. Consistently, IRF1 restricts the IL-9-dependent pathogenicity of Th9 cells in a mouse model of allergic asthma. Thus our study reveals that the molecular ratio between IRF4 and IRF1 balances Th9 fate, thus providing new possibilities for manipulation of Th9 differentiation. IFN-γ signalling inhibits production of IL-9, the defining cytokine of the Th9 cell subset. Here the authors show that IFN-γ does this by driving IRF1 to compete with IRF4 for Il9 promoter binding and skewing these cells towards a Th1 phenotype, an effect that reduces asthmatic inflammation in mice.