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The healing phase of contact hypersensitivity reactions is critically dependent on regulatory T cells (Tregs), but even the early inflammatory phase, that is, 6-24 hours after induction of a contact hypersensitivity reaction, is susceptible to Treg-mediated suppression. To investigate the underlying mechanisms, we injected Tregs before the challenge and analyzed the skin-infiltrating cells as early as 6 hours later. Early on, we found mainly neutrophils in the challenged skin, but only a few T cells. This influx of neutrophils was blocked by the injection of Tregs, indicating that they were able to prevent the first wave of leukocytes, which are responsible for starting an immune reaction. As an underlying mechanism, we identified that Tregs can tighten endothelial junctions by inducing intracellular cAMP, leading to protein kinase A-RhoA‒dependent signaling. This eventually reorganizes endothelial junction proteins, such as Notch3, Nectin 2, Filamin B, and VE-cadherin, all of which contribute to the tightening of the endothelial barrier. In summary, Tregs prevent the leakage of proinflammatory cells from and into the tissue, which establishes a mechanism to downregulate immune reactions.

The increase in the number of older adult drivers in developed countries has raised safety concerns due to the decline in their sensory, motor, perceptual, and cognitive abilities which can limit their driving capabilities. Their driving safety could be enhanced by the use of modern Automated Driver Assistance Systems (ADASs) and might totally resolved by full driving automation. However, the acceptance of these technologies by older adult drivers is not yet well understood. Thus, this study investigated older adult drivers’ intention to use six ADASs and full driving automation through two questionnaires with 115 and 132 participants respectively in Rhode Island, USA. A four-dimensional model referred to as the USEA model was used for exploring older adult drivers’ technology acceptance. The USEA model included perceived usefulness, perceived safety, perceived ease of use, and perceived anxiety. Path Analysis was applied to evaluate the proposed model. The results of this study identified the important factors in older adult drivers’ intention to use ADASs and full driving automation, which could assist stakeholders in improving technologies for use by older drivers.

Dendritic cells (DCs) are important inducers and regulators of T-cell responses. They are able to activate and modulate the differentiation of CD4+ and CD8+ T cells. In the skin, there are at least five phenotypically distinct DC subpopulations that can be distinguished by differential expression of the cell surface markers CD207, CD103, and CD11b. Previous studies have suggested that dermal CD11b−CD207+ conventional type 1 DCs are indispensable for the priming of a skin homing cytotoxic T-lymphocyte response. However, conventional type 1 DCs are also the only skin DC subset capable of cross-presenting exogenous antigens on major histocompatibility complex class I. Thus, it remained unclear whether for antigens that do not require cross-presentation, such as viruses that infect DCs, other DC subtypes in the skin can contribute to cytotoxic T-lymphocyte priming. To address this question, we used a transgenic mouse model that allows inducible expression and presentation of a model antigen on selected subsets of dermal DCs. We show that for antigens presented via the conventional major histocompatibility complex class I presentation pathway, CD207– dermal DCs are fully competent to prime a skin homing cytotoxic T-lymphocyte response that is capable of protection against a local virus challenge and gives rise to skin resident memory CD8+ T cells.

CD4 + CXCR5 + Foxp3 + T follicular regulatory (T FR ) cells control the germinal center responses. Like follicular helper T-cells, they express high levels of N uclear F actor of A ctivated T -cells c1 , predominantly its short isoform NFATc1/αA. Ablation of NFATc1 in Tregs prevents upregulation of CXCR5 and migration of T FR cells into B-cell follicles. By contrast, constitutive active NFATc1/αA defines the surface density of CXCR5, whose level determines how deep a T FR migrates into the GC and how effectively it controls antibody production. NFATc1/αA is necessary to overcome T FR -expressed B l ymphocyte- i nduced m aturation p rotein (Blimp-1), which can directly repress Cxcr5. Blimp-1 then reinforces the recruitment of NFATc1 to Cxcr5 by protein-protein interaction and by those means cooperates with NFATc1 for Cxcr5 transactivation. On the contrary, Blimp-1 is necessary to counterbalance NFATc1/αA, which strengthens the follicular development of Tregs, but bears the inherent risk of causing an ex-Treg phenotype.

NF-κB inducing kinase (NIK) is the key protein of the non-canonical NF-κB pathway and is important for the development of lymph nodes and other secondary immune organs. We elucidated the specific role of NIK in T cells using T-cell specific NIK-deficient (NIKΔT) mice. Despite showing normal development of lymphoid organs, NIKΔT mice were resistant to induction of CNS autoimmunity. T cells from NIKΔT mice were deficient in late priming, failed to up-regulate T-bet and to transmigrate into the CNS. Proteomic analysis of activated NIK-/- T cells showed de-regulated expression of proteins involved in the formation of the immunological synapse: in particular, proteins involved in cytoskeleton dynamics. In line with this we found that NIK-deficient T cells were hampered in phosphorylation of Zap70, LAT, AKT, ERK1/2 and PLCγ upon TCR engagement. Hence, our data disclose a hitherto unknown function of NIK in T-cell priming and differentiation.

Summary The gut microbiota affects remote organ functions but its impact on organotypic endothelial cell (EC) transcriptomes remains unexplored. The liver endothelium encounters microbiota-derived signals and metabolites via the portal circulation. To pinpoint how gut commensals affect the hepatic sinusoidal endothelium, a magnetic cell sorting protocol, combined with fluorescence-activated cell sorting, was used to isolate hepatic sinusoidal ECs from germ-free (GF) and conventionally raised (CONV-R) mice for transcriptome analysis by RNA sequencing. This resulted in a comprehensive map of microbiota-regulated hepatic EC-specific transcriptome profiles. Gene Ontology analysis revealed that several functional processes in the hepatic endothelium were affected. The absence of microbiota influenced the expression of genes involved in cholesterol flux and angiogenesis. Specifically, genes functioning in hepatic endothelial sphingosine metabolism and the sphingosine-1-phosphate pathway showed drastically increased expression in the GF state. Our analyses reveal a prominent role for the microbiota in shaping the transcriptional landscape of the hepatic endothelium., Graphical abstract, Highlights • Germ-free mice show transcriptome differences in the liver sinusoidal endothelium • Gut microbiota suppresses sphingolipid metabolism in the hepatic sinusoidal endothelium • Cholesterol flux and angiogenesis in liver endothelium is microbiota-regulated • Bacteroides thetaiotaomicron did not affect expression levels of the identified genes, Hepatology; Microbiome; Transcriptomics

OGG1 (8-oxoguanine-DNA glycosylase) is the major DNA repair glycosylase removing the premutagenic DNA base modification 8-oxo-7,8-dihydroguanine (8-oxoG) from the genome of mammalian cells. In addition, there is accumulating evidence that OGG1 and its substrate 8-oxoG might function in the regulation of certain genes, which could account for an attenuated immune response observed in Ogg1-/- mice in several settings. Indications for at least two different mechanisms have been obtained. Thus, OGG1 could either act as an ancillary transcription factor cooperating with the lysine-specific demethylase LSD1 or as an activator of small GTPases. Here, we analysed the activation by lipopolysaccaride (LPS) of primary splenocytes obtained from two different Ogg1-/- mouse strains. We found that the induction of TNF-α expression was reduced in splenocytes (in particular macrophages) of both Ogg1-/- strains. Notably, an inhibitor of LSD1, OG-L002, reduced the induction of TNF-α mRNA in splenocytes from wild-type mice to the level observed in splenocytes from Ogg1-/- mice and had no influence in the latter cells. In contrast, inhibitors of the MAP kinases p38 and JNK as well as the antioxidant N-acetylcysteine attenuated the LPS-stimulated TNF-α expression both in the absence and presence of OGG1. The free base 8-oxo-7,8-dihydroguanine had no influence on the TNF-α expression in the splenocytes. The data demonstrate that OGG1 plays a role in an LSD1-dependent pathway of LPS-induced macrophage activation in mice.

Background & Aims Liver sinusoidal endothelial cells (LSECs) are prominent liver-resident antigen (cross-)presenting cells. LSEC cross-priming of naive CD8 T cells does not require CD4 T cell help in contrast to priming by dendritic cells (DC) but leads to the formation of memory T cells that is preceded by transient Granzyme B (GzmB) expression. Here we provide evidence for a so far unrecognized CD4 T helper cell function in LSEC-induced CD8 T cell activation. Methods Naive CD8 T cells and differentiated T helper 1 (T h 1) cells were stimulated by antigen-presenting LSEC, and GzmB expression in CD8 T cells was determined by flow cytometry. To identify molecular pathways mediating this GzmB expression, mechanistic proof-of-concept experiments were conducted using stimulatory anti-CD3 antibody together with Hyper-IL-6. Results We demonstrate that LSECs simultaneously function in antigen co-presentation to CD8 and CD4 T cells. Such co-presentation revealed a function of T h 1 cells to increase GzmB expression in CD8 T cells after LSEC but not DC cross-priming. IL-2 released from T h 1 cells was required but not sufficient for rapid GzmB induction in CD8 T cells. T cell receptor together with IL-6 trans-signaling was necessary for IL-2 to mediate rapid GzmB induction. Conclusions Our findings indicate that LSECs can serve as a platform to facilitate CD4–CD8 T cell crosstalk enhancing the immune function of LSECs to cross-prime CD8 T cells. IL-6 trans-signaling-mediated responsiveness for IL-2 inducing sustained GzmB expression in CD8 T cells reveals unique mechanisms of CD4 T cell help and CD8 T cell differentiation through liver-resident antigen-presenting cells. Lay summary Our findings demonstrate that LSEC co-present antigen to CD8 and CD4 T cells and thereby enable CD4 T cell help for LSEC-priming of CD8 T cells. This CD4 T cell help selectively enhances the rapid upregulation of GzmB and effector function of LSEC-primed CD8 T cells thereby enhancing functional differentiation towards CD8 effector T cells.

Cylindromatosis (CYLD) is a ubiquitously expressed deubiquitinating enzyme which removes activating ubiquitin residues from important signaling molecules of the NF-κB pathway. In CYLDex7/8 transgenic mice, a naturally occurring short isoform (sCYLD) is overexpressed in the absence of full length CYLD, leading to excessive NF-κB activity. Herein, we investigated the impact of the CYLDex7/8 mutation selectively in T cells on the development of experimental allergic airway disease induced by sensitization and challenge with ovalbumin. Compared with their wildtype littermates, mice bearing the T cell-specific mutation (CD4+CYLDex7/8) display stronger eosinophilia and mucus production in the lungs and higher IgE serum levels. The reason for these observations is excessive production of T cell-derived IL-9, a cytokine to whom allergy-promoting properties were ascribed. Consequently, blockade of IL-9 in CD4+CYLDex7/8 mice alleviates the development of disease symptoms. Thus, by polarization of the T cell cytokine response, sCYLD can favor the development of allergic airway disease.

Summary Environmental signals shape host physiology and fitness. Microbiota-derived cues are required to program conventional dendritic cells (cDCs) during the steady state so that they can promptly respond and initiate adaptive immune responses when encountering pathogens. However, the molecular underpinnings of microbiota-guided instructive programs are not well understood. Here, we report that the indigenous microbiota controls constitutive production of type I interferons (IFN-I) by plasmacytoid DCs. Using genome-wide analysis of transcriptional and epigenetic regulomes of cDCs from germ-free and IFN-I receptor (IFNAR)-deficient mice, we found that tonic IFNAR signaling instructs a specific epigenomic and metabolic basal state that poises cDCs for future pathogen combat. However, such beneficial biological function comes with a trade-off. Instructed cDCs can prime T cell responses against harmless peripheral antigens when removing roadblocks of peripheral tolerance. Our data provide fresh insights into the evolutionary trade-offs that come with successful adaptation of vertebrates to their microbial environment.

SummaryDuring early embryogenesis, microglia arise from yolk sac progenitors that populate the developing central nervous system (CNS), but how the tissue-resident macrophages are maintained throughout the organism’s lifespan still remains unclear. Here, we describe a system that allows specific, conditional ablation of microglia in adult mice. We found that the microglial compartment was reconstituted within 1 week of depletion. Microglia repopulation relied on CNS-resident cells, independent from bone-marrow-derived precursors. During repopulation, microglia formed clusters of highly proliferative cells that migrated apart once steady state was achieved. Proliferating microglia expressed high amounts of the interleukin-1 receptor (IL-1R), and treatment with an IL-1R antagonist during the repopulation phase impaired microglia proliferation. Hence, microglia have the potential for efficient self-renewal without the contribution of peripheral myeloid cells, and IL-1R signaling participates in this restorative proliferation process.

Immunologic approaches to combat cancer aim at the induction of tumor-reactive immune responses to achieve long-term protection. In this context, we recently developed a transcutaneous immunization (TCI) method using the Toll-like receptor (TLR) 7 agonist imiquimod and a peptide epitope. Application onto intact skin induces potent cytotoxic T lymphocyte (CTL) responses and protection against transplanted tumors. The purpose of this study was to explore the effects of UV irradiation on imiquimod-based TCI. Here we show that skin exposure to low-dose UV light before TCI with imiquimod strongly boosts specific CTL responses leading to memory formation and enhanced tumor protection. Toward the mechanisms, we show that the activation of bone-marrow-derived dermal dendritic cells (DCs), but not Langerin-expressing DCs, is responsible for enhanced CTL activation. We describe an optimized TCI method that mediates enhanced CTL and antitumor responses by a DC- and TLR-dependent mechanism. These data may provide the basis for the future development of advanced vaccination protocols against tumors and persistent virus infections.

In humans and mice naturally occurring regulatory T cells (nTregs) are crucial for the maintenance of peripheral tolerance by controlling not only potentially autoreactive T cells but virtually all cells of the adaptive and innate immune system. Here we show that co-culture of murine dendritic cells (DC) and nTregs results in an immediate increase of cAMP in DC, responsible for a rapid down-regulation of co-stimulatory molecules (CD80, CD86). In addition, the inhibitory surface molecule B7-H3 on DC is up-regulated. Subsequently, nTreg-derived IL-10 inhibits the cytokine production (IL-6, IL-12) of suppressed DC therewith preserving their silent phenotype. Hence, our data indicate that nTregs effectively control exuberant immune responses by directly limiting the stimulatory capacity of DC via a sophisticated chronologic action of inhibitory signals.

Elevated intracellular cyclic AMP levels, which suppress the proliferation of naive T cells and type 1 T helper (Th1) cells are a property of T helper 2 (Th2) cells and regulatory T cells. While cyclic AMP signals interfere with the IL-2 promoter induction, they support the induction of Th2-type genes, in particular of il-5 gene. We show here that cyclic AMP signals support the generation of three inducible DNase I hypersensitive chromatin sites over the il-5 locus, including its promoter region. In addition, cyclic AMP signals enhance histone H3 acetylation at the IL-5 promoter and the concerted binding of GATA-3 and NFATc to the promoter. This is facilitated by direct protein-protein interactions involving the C-terminal Zn2+-finger of GATA-3 and the C-terminal region of the NFATc1 DNA binding domain. Because inhibition of NFATc binding to the IL-5 promoter in vivo also affects the binding of GATA-3, one may conclude that upon induction of Th2 effector cells NFATc recruits GATA-3 to Th2-type genes. These data demonstrate the functional importance of cyclic AMP signals for the interplay between GATA-3 and NFATc factors in the transcriptional control of lymphokine expression in Th2 effector cells.

Obesity and type 2 diabetes are associated with metabolic defects and adipose tissue inflammation. Foxp3(+) regulatory Tcells (Tregs) control tissue homeostasis by counteracting local inflammation. However, if and how Tcells interlink environmental influences with adipocyte function remains unknown. Here, we report that enhancing sympathetic tone by cold exposure, beta3-adrenergic receptor (ADRB3) stimulation or a short-term high-calorie diet enhances Treg induction invitro and invivo. CD4(+) Tcell proteomes revealed higher expression of Foxp3 regulatory networks in response to cold or ADRB3 stimulation invivo reflecting Treg induction. Specifically, Ragulator-interacting protein C17orf59, which limits mTORC1 activity, was upregulated in CD4(+) Tcells by either ADRB3 stimulation or cold exposure, suggesting contribution to Treg induction. By loss- and gain-of-function studies, including Treg depletion and transfers invivo, we demonstrated that a Tcell-specific Stat6/Pten axis links cold exposure or ADRB3 stimulation with Foxp3(+) Treg induction and adipose tissue function. Our findings offer a new mechanistic model in which tissue-specific Tregs maintain adipose tissue function.

Inducible cAMP early repressor (ICER) is a transcriptional repressor, which, because of alternate promoter use, is generated from the 3′ region of the cAMP response modulator (CREM) gene. Its expression and nuclear occurence are elevated by high cAMP levels in naturally occurring regulatory T cells (nTregs). Using two mouse models, we demonstrate that nTregs control the cellular localization of ICER/CREM, and thereby inhibit IL-2 synthesis in conventional CD4+ T cells. Ablation of nTregs in depletion of regulatory T cell (DEREG) mice resulted in cytosolic localization of ICER/CREM and increased IL-2 synthesis upon stimulation. Direct contacts between nTregs and conventional CD4+ T cells led to nuclear accumulation of ICER/CREM and suppression of IL-2 synthesis on administration of CD28 superagonistic (CD28SA) Ab. In a similar way, nTregs communicated with B cells and induced the cAMP-driven nuclear localization of ICER/CREM. High levels of ICER suppressed the induction of nuclear factor of activated T cell c1 (NFATc1) gene in T cells whose inducible Nfat c1 P1 promoter bears two highly conserved cAMP-responsive elements to which ICER/CREM can bind. These findings suggest that nTregs suppress T-cell responses by the cAMP-dependent nuclear accumulation of ICER/CREM and inhibition of NFATc1 and IL-2 induction. Moreover, function and/or depletion of nTregs may play an important role in antitumor therapy since B16 melanoma is inhibited by ICER knock-out mice.

Dimethyl fumarate (DMF), a fumaric acid ester with potential immunomodulatory and neuroprotective effect, was recently approved as treatment for relapsing–remitting multiple sclerosis (MS). DMF ameliorates the clinical course of experimental autoimmune encephalomyelitis (EAE), the murine model of MS, where it exerts a neuroprotective action, reducing demyelination and axonal loss. We hypothesized that these effects are mediated, at least in part, through its action on microglia. We used a microglial cell line (N9) activated with lipopolysaccharide (LPS) to analyze the effect of monomethyl fumarate (MMF), a bioactive metabolite of DMF, in vitro. We show that MMF reverts the molecular phenotype of LPS-activatedmicroglia from pro(M1-like) to anti(M2-like) inflammatory. Thus, MMF significantly reduced production and expression of neurotoxic molecules, TNF-alpha, IL1-beta and iNOS, by activated microglia, while significantly increasing the production of receptors typically expressed by alternatively activated microglia, NURR1, CD200R and CX3CR1. We validated MMF effect at functional level, with the observation that MMF increases microglial internal calcium concentration and phagocytosis, itself associated with an increased expression of TREM2, which facilitates debris clearance in the absence of inflammation. Previous studies suggest thatMMF effects are related to activation of the Nrf2-anti-oxidant pathway; however such a possibility may not account for inhibitory effects on pro-inflammatory cytokines in microglia. In line with the observation that MMF upregulates NURR1, a molecule involved in inhibition of NFkB, we postulated that MMF exerts its anti-inflammatory effect through inhibiting NFkB. MMF is an agonist of HCA2 and activation of this receptor leads to an increase in intracellular Ca2+, which we observed upon exposure of activated microglia to MMF. We therefore addressed the possibility that MMF could signal through binding to HCA2.We show that HCA2 is expressed onN9 and blocking HCA2 reverts the effect ofMMF on the expression of pro-inflammatory cytokines and of NURR1. We have postulated and validated a downstream pathway activated by internal Ca2+ increase induced through MMF binding to HCA2, which leads to inhibition of NFkB activation by de-acetylation via the AMPK/Sirt axis. We show in vivo and ex vivo that treatment of EAE-affected mice with DMF upregulates M2-phenotype markers in the brain, and confirm the neuroprotective effect of MMF.