Differential effects of IFN-β on IL-12, IL-23, and IL-10 expression in TLR-stimulated dendritic cells

Interferon-β modulates microglial polarization to ameliorate delayed tPA-exacerbated brain injury in ischemic stroke

Tissue plasminogen activator (tPA) is the only FDA-approved drug for the treatment of ischemic stroke. Delayed tPA administration is associated with increased risks of blood-brain barrier (BBB) disruption and hemorrhagic transformation. Studies have shown that interferon beta (IFNβ) or type I IFN receptor (IFNAR1) signaling confers protection against ischemic stroke in preclinical models. In addition, we have previously demonstrated that IFNβ can be co-administered with tPA to alleviate delayed tPA-induced adverse effects in ischemic stroke. In this study, we investigated the time limit of IFNβ treatment on the extension of tPA therapeutic window and assessed the effect of IFNβ on modulating microglia (MG) phenotypes in ischemic stroke with delayed tPA treatment. Mice were subjected to 40 minutes transient middle cerebral artery occlusion (MCAO) followed by delayed tPA treatment in the presence or absence of IFNβ at 3h, 4.5h or 6h post-reperfusion. In addition, mice with MG-specific IFNAR1 knockdown were generated to validate the effects of IFNβ on modulating MG phenotypes, ameliorating brain injury, and lessening BBB disruption in delayed tPA-treated MCAO mice. Our results showed that IFNβ extended tPA therapeutic window to 4.5h post-reperfusion in MCAO mice, and that was accompanied with attenuated brain injury and lessened BBB disruption. Mechanistically, our findings revealed that IFNβ modulated MG polarization, leading to the suppression of inflammatory MG and the promotion of anti-inflammatory MG, in delayed tPA-treated MCAO mice. Notably, these effects were abolished in MG-specific IFNAR1 knockdown MCAO mice. Furthermore, the protective effect of IFNβ on the amelioration of delayed tPA-exacerbated ischemic brain injury was also abolished in these mice. Finally, we identified that IFNβ-mediated modulation of MG phenotypes played a role in maintaining BBB integrity, because the knockdown of IFNAR1 in MG partly reversed the protective effect of IFNβ on lessening BBB disruption in delayed tPA-treated MCAO mice. In summary, our study reveals a novel function of IFNβ in modulating MG phenotypes, and that may subsequently confer protection against delayed tPA-exacerbated brain injury in ischemic stroke.

Heat shock protein 40 of Streptococcus pneumoniae induces immune response of human dendritic cells via TLR4-dependent p38 MAPK and JNK signaling pathways

INTRODUCTION

Heat shock protein 40 (HSP40) is a vaccine adjuvant candidate for Streptococcus pneumoniae. The mechanism by which HSP40 activates the human dendritic cells (DCs) is unclear.

METHODS

DCs were isolated from human peripheral blood and their markers (HLA-DR, CD86, CD83, and CD80) were detected by flow cytometry. The messenger RNA (mRNA) and secretion levels of inflammary cytokines were measured after DCs were stimulated with recombinant HSP40 (rHSP40). Short hairpin RNAs were used to knock down toll-like receptor 2 (TLR2) and TLR4. The TLR2- or TLR4-deficient DCs were treated with lipopolysaccharides, rHSP40, or peptidoglycan, and then the secretion levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured. Moreover, the secretion levels of TNF-α and IL-6 were measured after DCs were treated with mitogen-activated protein kinase (MAPK) inhibitors including SB203580, SP600125, and U0126. In addition, the phosphorylation levels of p38 MAPK and Jun N-terminal kinase (JNK) in DC cells were determined using western blot analysis after treatment with rHSP40 for different times.

RESULTS

DCs were successfully isolated and cultured. rHSP40 treatment significantly increased cytokine levels in a concentration-dependent manner. TLR4 deficiency, but not TLR2 deficiency, significantly suppressed the rHSP40-induced secretion of tumor necrosis factor-α  (TNF-α) and interleukin-6 (IL-6). SB203580 and SP600125 significantly inhibited the rHSP40-induced secretion of TNF-α and IL-6. rHSP40 significantly enhanced the phosphorylation of p38 MAPK and JNK.

CONCLUSION

HPS40 stimulates the immune response of DCs via the p38 MAPK and JNK signaling pathways, which depend on TLR4.

IFN-κ Is a Rheostat for Development of Psoriasiform Inflammation

Psoriasis is a common, inflammatory autoimmune skin disease. Early detection of an IFN-1 signature occurs in many psoriasis lesions, but the source of IFN production remains debated. IFN-κ is an important source of IFN-1 production in the epidermis. We identified a correlation between IFN-regulated and psoriasis-associated genes in human lesional skin. We thus wanted to explore the effects of IFN-κ in psoriasis using the well-characterized imiquimod psoriasis model. Three mouse strains aged 10 weeks were used: wild-type C57Bl/6, C57Bl/6 that overexpress Ifnk in the epidermis (i.e., transgenic), and total body Ifnk^-/- (i.e., knockout) strain. Psoriasis was induced by topical application of imiquimod on both ears for 8 consecutive days. Notably, the severity of skin lesions and inflammatory cell infiltration was more significantly increased in transgenic than in wild-type than in knockout mice. Gene expression analysis identified greater upregulation of Mxa, Il1b, Tnfa, Il6, Il12, Il23, Il17, and Ifng in transgenic compared to wild-type compared to knockout mice after imiquimod treatment. Furthermore, imiquimod increased CD8⁺ and CD4⁺ T-cell infiltration more in transgenic than in wild-type than in knockout mice. In summary, we identified IFN-κ as a rheostat for initiation of psoriasiform inflammation. This suggests that targeting IFN-1s early in the disease may be an effective way of controlling psoriatic inflammation.

Caffeine Has Different Immunomodulatory Effect on the Cytokine Expression and NLRP3 Inflammasome Function in Various Human Macrophage Subpopulations

Besides its well-known psychoactive effects, caffeine has a broad range of actions. It regulates several physiological mechanisms as well as modulates both native and adaptive immune responses by various ways. Although caffeine is assumed to be a negative regulator of inflammation, the effect on the secretion of pro- and anti-inflammatory cytokines is highly controversial. Macrophages are major mediators of inflammatory responses; however, the various subpopulations develop different effects ranging from the initiation to the resolution of inflammation. Here we report a comparative analysis of the effect of caffeine on two subpopulations of human monocyte-derived macrophages differentiated in the presence of macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF), resulting in M-MΦs and GM-MΦs, respectively. We showed that although TNF-α secretion was downregulated in both LPS-activated MΦ subtypes by caffeine, the secretion of IL-8, IL-6, and IL-1β as well as the expression of Nod-like receptors was enhanced in M-MΦs, while it did not change in GM-MΦs. We showed that caffeine (1) altered adenosine receptor expression, (2) changed Akt/AMPK/mTOR signaling pathways, and (3) inhibited STAT1/IL-10 signaling axis in M-MΦs. We hypothesized that these alterations play an important modulatory role in the upregulation of NLRP3 inflammasome-mediated IL-1β secretion in LPS-activated M-MΦs following caffeine treatment.

A Hepatitis B Virus-Derived Peptide Can Inhibit Infection of Human Lung Cells with SARS-CoV-2 in a Type-1 Interferon-Dependent Manner

The current COVID-19 pandemic has highlighted the urgent need to develop effective therapeutic strategies. We evaluated the in vitro antiviral effect against SARS-CoV-2 of a hepatitis B virus (HBV) hexamer peptide, Poly6, which is capable of eliciting an antiviral effect against human immunodeficiency virus -1 (HIV-1), as a novel HIV-1 integrase inhibitor, and a strong anticancer immune response in an IFN-I-dependent manner, as a novel potential adjuvant in anticancer immunotherapy. Here, we report that Poly6 exerts an anti-SARS-CoV-2 effect, with an estimated 50% inhibitory concentration of 2.617 µM, in the human bronchial epithelial cell line, Calu-3 but not in Vero-E6 cells, which are deficient in type 1 interferon (IFN-I) signaling. We proved via assays based on mRNA profiles, inhibitors, or blocking antibodies that Poly6 can exert an anti-SARS-CoV-2 effect in an IFN-I-dependent manner. We also found that Poly6 inhibits IL-6 production enhanced by SARS-CoV-2 in infected Calu-3 cells at both the transcription and the translation levels, mediated via IL-10 induction in an IFN-I-dependent manner. These results indicate the feasibility of Poly6 as an IFN-I-inducing COVID-19 drug with potent antiviral and anti-inflammatory activities.

PI3K, mTOR and GSK3 modulate cytokines' production in peripheral leukocyte in temporal lobe epilepsy

INTRODUCTION

Epilepsy is a common pathological condition that predisposes individuals to seizures, as well as cognitive and emotional dysfunctions. Different studies have demonstrated that inflammation contributes to the pathophysiology of epilepsy. Indeed, seizures change the peripheral inflammatory pattern, which, in turn, could contribute to seizures. However, the cause of the altered production of peripheral inflammatory mediators is not known. The PI3K/mTOR/GSK3β pathway is important for different physiological and pharmacological phenomena. Therefore, in the present study, we tested the hypothesis that the PI3K/mTOR/GSK3β pathway is deregulated in immune cells from patients with epilepsy and contributes to the abnormal production of inflammatory mediators.

METHODS

Patients with temporal lobe epilepsy presenting hippocampal sclerosis and controls aged between 18 and 65 years-old were selected for this study. Peripheral blood was collected for the isolation of peripheral mononuclear blood cells (PBMC). Cells were pre-incubated with different PI3K, mTOR and GSK-3 inhibitors for 30 min and further stimulated with phytohaemaglutinin (PHA) or vehicle for 24 h. The supernatant was used to evaluate the production of IL-1β, IL-6, IL-10, TNF e IL-12p70.

RESULTS

Non-selective inhibition of PI3K, as well as inhibition of PI3Kγ and GSK-3, reduced the levels of TNF and IL-10 in PHA-stimulated cells from TLE individuals. This stimulus increased the production of IL-12p70 only in cells from TLE individuals, while the inhibition of PI3K and mTOR enhanced the production of this cytokine. On the other hand, inhibition of GSK3 reduced the PHA-induced production of IL-12p70.

CONCLUSIONS

Herein we demonstrated that the production of cytokines by immune cells from patients with TLE differs from non-epileptic patients. This differential regulation may be associated with the altered activity and responsiveness of intracellular molecules, such as PI3K, mTOR and GSK-3, which, in turn, might contribute to the inflammatory state that exists in epilepsy and its pathogenesis.

GSK3: A Kinase Balancing Promotion and Resolution of Inflammation

GSK3 has been implicated for years in the regulation of inflammation and addressed in a plethora of scientific reports using a variety of experimental (disease) models and approaches. However, the specific role of GSK3 in the inflammatory process is still not fully understood and controversially discussed. Following a detailed overview of structure, function, and various regulatory levels, this review focusses on the immunoregulatory functions of GSK3, including the current knowledge obtained from animal models. Its impact on pro-inflammatory cytokine/chemokine profiles, bacterial/viral infections, and the modulation of associated pro-inflammatory transcriptional and signaling pathways is discussed. Moreover, GSK3 contributes to the resolution of inflammation on multiple levels, e.g., via the regulation of pro-resolving mediators, the clearance of apoptotic immune cells, and tissue repair processes. The influence of GSK3 on the development of different forms of stimulation tolerance is also addressed. Collectively, the role of GSK3 as a kinase balancing the initiation/perpetuation and the amelioration/resolution of inflammation is highlighted.

NCoR1: Putting the Brakes on the Dendritic Cell Immune Tolerance

Understanding the mechanisms fine-tuning immunogenic versus tolerogenic balance in dendritic cells (DCs) is of high importance for therapeutic approaches. We found that NCoR1-mediated direct repression of the tolerogenic program in conventional DCs is essential for induction of an optimal immunogenic response. NCoR1 depletion upregulated a wide variety of tolerogenic genes in activated DCs, which consequently resulted in increased frequency of FoxP3⁺ regulatory T cells. Mechanistically, NCoR1 masks the PU.1-bound super-enhancers on major tolerogenic genes after DC activation that are subsequently bound by nuclear factor-κB. NCoR1 knockdown (KD) reduced RelA nuclear translocation and activity, whereas RelB was unaffected, providing activated DCs a tolerogenic advantage. Moreover, NCoR1^DC−/- mice depicted enhanced Tregs in draining lymph nodes with increased disease burden upon bacterial and parasitic infections. Besides, adoptive transfer of activated NCoR1 KD DCs in infected animals showed a similar phenotype. Collectively, our results demonstrated NCoR1 as a promising target to control DC-mediated immune tolerance.

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NCoR1 directly represses tolerogenic program in mouse cDCs

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Depletion of NCoR1 in cDCs enhanced Treg development ex vivo and in vivo

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NCoR1 masks PU.1-bound super-enhancers on tolerogenic genes in cDCs

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NCoR1^DC−/− animals depicted enhanced Treg frequency and infection load

The cytokine network type I IFN-IL-27-IL-10 is augmented in murine and human lupus

IL-10 is elevated in the autoimmune disease systemic lupus erythematosus (SLE). Here, we show that conventional dendritic cells (cDCs) from predisease lupus-prone B6.NZM Sle1/Sle2/Sle3 triple congenic (TCSle) mice produce more IL-10 than wild-type congenic cDCs upon TLR stimulation, and this overproduction is prevented by blocking the type I IFN receptor (IFNAR) with specific Abs. Priming wild-type cDCs with type I IFN mimics the IL-10 overproduction of TCSle cDCs. The MAPK ERK is more phosphorylated in lupus cDCs, partially contributing to IL-10 overproduction. Moreover, we found that TCSle cDCs express higher levels of IL-27 upon TLR7/TLR9 stimulation, and IFNAR blockade reduced IL-27 levels in TCSle cDCs. These results suggest that dysregulated type I IFNs in cDCs contribute to the increased IL-10 and IL-27 in SLE. Since IL-27 neutralization did not inhibit TLR-induced IL-10 production, we propose that type I IFNs enhanced IL-10 in TCSle cDCs independently from IL-27. Moreover, RNA sequencing analysis of a cohort of SLE patients reveals higher gene expression of these cytokines in SLE patients expressing a high IFN signature. Since IL-27 and IL-10 have both pro- and anti-inflammatory effects, our results also suggest that these cytokines can be modulated by the therapeutic IFN blockade in trials in SLE patients and have complex effects on the autoimmune response.

IFN-β Plays Both Pro- and Anti-inflammatory Roles in the Rat Cardiac Fibroblast Through Differential STAT Protein Activation

Cardiac fibroblasts (CFs) contribute to theinflammatory response to tissue damage, secreting both pro- and anti-inflammatory cytokines and chemokines. Interferon beta (IFN-β) induces the phosphorylation of signal transducer and activator of transcription (STAT) proteins through the activation of its own receptor, modulating the secretion of cytokines and chemokines which regulate inflammation. However, the role of IFN-β and STAT proteins in modulating the inflammatory response of CF remains unknown. CF were isolated from adult male rats and subsequently stimulated with IFN-β to evaluate the participation of STAT proteins in secreting chemokines, cytokines, cell adhesion proteins expression and in their capacity to recruit neutrophils. In addition, in CF in which the TRL4 receptor was pre-activated, the effect of INF-β on the aforementioned responses was also evaluated. Cardiac fibroblasts stimulation with IFN-β showed an increase in STAT1, STAT2, and STAT3 phosphorylation. IFN-β stimulation through STAT1 activation increased proinflammatory chemokines MCP-1 and IP-10 secretion, whereas IFN-β induced activation of STAT3 increased cytokine secretion of anti-inflammatory IL-10. Moreover, in TLR4-activated CF, IFN-β through STAT2 and/or STAT3, produced an anti-inflammatory effect, reducing pro-IL-1β, TNF-α, IL-6, MCP-1, and IP-10 secretion; and decreasing neutrophil recruitment by decreasing ICAM-1 and VCAM-1 expression. Altogether, our results indicate that IFN-β exerts both pro-inflammatory and anti-inflammatory effects in non-stimulated CF, through differential activation of STAT proteins. When CF were previously treated with an inflammatory agent such as TLR-4 activation, IFN-β effects were predominantly anti-inflammatory.

Naturally produced type I IFNs enhance human myeloid dendritic cell maturation and IL-12p70 production and mediate elevated effector functions in innate and adaptive immune cells

There has recently been a paradigm shift in the field of dendritic cell (DC)-based immunotherapy, where several clinical studies have confirmed the feasibility and advantageousness of using directly isolated human blood-derived DCs over in vitro differentiated subsets. There are two major DC subsets found in blood; plasmacytoid DCs (pDCs) and myeloid DCs (mDCs), and both have been tested clinically. CD1c⁺ mDCs are highly efficient antigen-presenting cells that have the ability to secrete IL-12p70, while pDCs are professional IFN-α-secreting cells that are shown to induce innate immune responses in melanoma patients. Hence, combining mDCs and pDCs poses as an attractive, multi-functional vaccine approach. However, type I IFNs have been reported to inhibit IL-12p70 production and mDC-induced T-cell activation. In this study, we investigate the effect of IFN-α on mDC maturation and function. We demonstrate that both recombinant IFN-α and activated pDCs strongly enhance mDC maturation and increase IL-12p70 production. Co-cultured mDCs and pDCs additionally have beneficial effect on NK and NKT-cell activation and also enhances IFN-γ production by allogeneic T cells. In contrast, the presence of type I IFNs reduces the proliferative T-cell response. The mere presence of a small fraction of activated pDCs is sufficient for these effects and the required ratio between the subsets is non-stringent. Taken together, these results support the usage of mDCs and pDCs combined into one immunotherapeutic vaccine with broad immunostimulatory features.

The influence of interferon-β supplemented human dendritic cells on BCG immunogenicity

INTRODUCTION

Tuberculosis (TB) remains a huge worldwide burden, despite extensive vaccination coverage with the Bacillus Calmette-Guérin (BCG), the only vaccine available against this disease, indicating that BCG-driven immunity is inadequate to protect the human population against TB. This underscore the critical necessitate to develop an improved TB vaccine, based on a better understanding of host-pathogen interactions and immune responses during mycobacterial infection.

AIM OF THE WORK

To examine whether the exogenous addition of IFN-β could improve dendritic cell (DC) response to Mycobacterium bovis (M. bovis) and to evaluate the effect induced by the infection of human DCs with M. bovis (with and without IFN-β) and Mycobacterium tuberculosis (Mtb) on DC viability as well as to compare the ability of BCG and Mtb to provide DCs with a Th1-polarizing capacity through the assessment of the immunoregulatory cytokines interleukin (IL)-12, IL-10 and interferon-gamma (IFN-γ).

METHODS

Immature DCs (iDCs) were generated in vitro using peripheral blood monocytes separated by anti-CD14-conjugated microbeads in the presence of granulocyte-macrophage-colony-stimulating factor (GM-CSF) and IL-4, cultured cells were analyzed using flow cytometry, then we tested DC viability after inoculation with M. bovis (with and without IFN-β pretreatment) and Mtb using light microscopic examination and trypan blue exclusion method. Additionally, supernatants from infected-DCs cultures were analyzed for IFN-γ, IL-12 and IL-10 by ELISA.

RESULTS

The viability of BCG-infected DCs was significantly higher than that of Mtb-infected DCs (61.55% vs 52.10%). BCG-infected DC produced significantly more IL-12 (p = 0.02) and less IL-10 (p = 0.01) compared with Mtb-infected cells. IFN-β-pretreated BCG-infected DCs produced significantly larger amounts of IL-12 than did BCG-infected DCs (p = 0.03) and Mtb-infected cells (p < 0.001).

CONCLUSION

IFN-β improves DC functions following BCG infection, thus assuming that IFN-β could be used as a vaccine adjuvant.

Breaking self-tolerance during autoimmunity and cancer immunity: Myeloid cells and type I IFN response regulation

The generation and regulation of innate immune signals are key determinants of autoimmune pathogenesis. Emerging evidence suggests that parallel processes operating in the setting of solid tumors can similarly determine the balance between tolerance and immunity and ultimately the effectiveness of the antitumor immune response. In both contexts, self-specific responses start with innate immune cell activation that leads to the initial break in self-tolerance, which can be followed by immune response amplification and maturation through innate-adaptive crosstalk, and finally immune-mediated tissue/tumor destruction that can further potentiate inflammation. Of particular importance for these processes is type I IFN, which is induced in response to endogenous ligands, such as self-nucleic acids, and acts on myeloid cells to promote the expansion of autoreactive or tumor-specific T cells and their influx into the target tissue. Evidence from the study of human disease pathophysiology and genetics and mouse models of disease has revealed an extensive and complex network of negative regulatory pathways that has evolved to restrain type I IFN production and activity. Here, we review the overlapping features of self- and tumor-specific immune responses, including the central role that regulators of the type I IFN response and innate immune cell activation play in maintaining tolerance, and discuss how a better understanding of the pathophysiology of autoimmunity can help to identify new approaches to promote immune-mediated tumor destruction.

Mitochondrial dynamics controls anti-tumour innate immunity by regulating CHIP-IRF1 axis stability

Macrophages, dendritic cells and other innate immune cells are involved in inflammation and host defense against infection. Metabolic shifts in mitochondrial dynamics may be involved in Toll-like receptor agonist-mediated inflammatory responses and immune cell polarization. However, whether the mitochondrial morphology in myeloid immune cells affects anti-tumor immunity is unclear. Here we show that FAM73b, a mitochondrial outer membrane protein, has a pivotal function in Toll-like receptor-regulated mitochondrial morphology switching from fusion to fission. Switching to mitochondrial fission via ablation of Fam73b (also known as Miga2) promotes IL-12 production. In tumor-associated macrophages, this switch results in T-cell activation and enhances anti-tumor immunity. We also show that the mitochondrial morphology affects Parkin expression and its recruitment to mitochondria. Parkin controls the stability of the downstream CHIP–IRF1 axis through proteolysis. Our findings identify mechanisms associated with mitochondrial dynamics that control anti-tumor immune responses and that are potential targets for cancer immunotherapy.

Macrophage metabolism controls differentiation and subsequent adaptive immune responses. Here the authors show that mitochondrial membrane protein Fam73b regulates TLR-mediated mitochondrial switching of fusion to fission to induce IL-12 production via accumulation of Parkin and stabilization of IRF1 in macrophages, resulting in control of anti-tumor immunity in mice.

Interferon-β regulates dendritic cell activation and migration in experimental autoimmune encephalomyelitis

CD11c⁺ dendritic cells (DCs) exert a critical role as antigen-presenting cells in regulating pathogenic T cells in multiple sclerosis (MS). To determine whether the therapeutic benefit of interferon-β (IFN-β) treatment for MS is in part influenced by IFN regulation of DC function, we examined the immunophenotype of DCs derived from IFN-β^+/+ and IFN-β^-/- mice using a myelin oligodendrocyte glycoprotein (MOG) peptide-induced mouse model of MS, experimental autoimmune encephalomyelitis (EAE). Our earlier work identified that IFN-β^-/- mice exhibit earlier onset and more rapid progression of neurological impairment compared with IFN-β^+/+ mice. In this study we show that lipopolysaccharide-/MOG peptide-stimulated IFN-β^-/- DCs secrete cytokines associated with pathological T helper type 17 rather than regulatory T-cell polarization and exhibit increased CD80 and MHCII expression when compared with stimulated IFN-β^+/+ DCs. IFN-β^-/- DCs from mice immunized to develop EAE induce greater proliferation of MOG-transgenic CD4⁺ T cells and promote interleukin-17 production by these T cells. Adoptive transfer of MOG peptide-primed IFN-β^-/- DCs into IFN-β^+/+ and IFN-β^-/- mice immunized to develop EAE resulted in their rapid migration into the central nervous system of recipient mice, before onset of disease, which we attribute to failed signal transducer and activator of transcription 1-mediated inhibition of CCR7. Taken together, our data support immunoregulatory roles for IFN-β in the activation and migration of DCs during EAE.

Intact Pneumococci Trigger Transcription of Interferon-Related Genes in Human Monocytes, while Fragmented, Autolyzed Bacteria Subvert This Response

A peculiar trait of pneumococci (Streptococcus pneumoniae) is their propensity to undergo spontaneous lysis during stationary growth due to activation of the enzyme autolysin (LytA), which fragments the peptidoglycan cell wall. The fragments that are generated upon autolysis impair phagocytosis and reduce production of interleukin-12 (IL-12) and gamma interferon (IFN-γ) by human leukocytes in response to intact pneumococci, thereby impeding crucial host defenses. The objective was to identify additional monocyte genes whose transcription is induced by intact pneumococci and subverted by autolyzed bacteria. Monocytes were isolated from healthy blood donors and stimulated for 3 h with UV-inactivated S. pneumoniae (Rx1PLY^- LytA⁺ strain), which is capable of autolyzing, its LytA^- isogenic autolysin-deficient mutant, or a mixture of the two (containing twice the initial bacterial concentration). Gene expression was assessed by Illumina microarray, and selected findings were confirmed by reverse transcription-quantitative real-time PCR (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), and flow cytometry. In all, we identified 121 genes that were upregulated to a significantly higher degree by intact than autolyzed pneumococci. These included IFNB1 and a large set of interferon-induced genes, such as IFIT3, RSAD2, CFCL1, and CXCL10 genes, as well as IL12B and CD40 genes. RT-qPCR revealed that transcription of these genes in response to intact pneumococci diminished when autolyzed pneumococci were admixed and that this pattern was independent of pneumolysin. Thus, transcription of interferon-related genes is triggered by intact pneumococci and subverted by fragments generated by spontaneous bacterial autolysis. We suggest that interferon-related pathways are important for elimination of pneumococci and that autolysis contributes to virulence by extinguishing these pathways.

Dendritic cells in central nervous system autoimmunity

Dendritic cells (DCs) operate at the intersection of the innate and adaptive immune systems. DCs can promote or inhibit adaptive immune responses against neuroantigens. While DC intrinsic properties, i.e., their maturation state or the subset they belong to, are important determinants of the outcome of an autoimmune reaction, tissue-specific cues might also be relevant for the function of DCs. Thus, a better understanding of the performance of distinct DC subsets in specific anatomical niches, not only in lymphoid tissue but also in non-lymphoid tissues such as the meninges, the choroid plexus, and the inflamed CNS parenchyma, will be instrumental for the design of immune intervention strategies to chronic inflammatory diseases that do not put at risk basic surveillance functions of the immune system in the CNS. Here, we will review modern concepts of DC biology in steady state and during autoimmune neuroinflammation.

Interferon-β Modulates Inflammatory Response in Cerebral Ischemia

BACKGROUND

Stroke is a leading cause of death in the world. In >80% of strokes, the initial acute phase of ischemic injury is due to the occlusion of a blood vessel resulting in severe focal hypoperfusion, excitotoxicity, and oxidative damage. Interferon-β (IFNβ), a cytokine with immunomodulatory properties, was approved by the US Food and Drug Administration for the treatment of relapsing-remitting multiple sclerosis for more than a decade. Its anti-inflammatory properties and well-characterized safety profile suggest that IFNβ has therapeutic potential for the treatment of ischemic stroke.

METHODS AND RESULTS

We investigated the therapeutic effect of IFNβ in the mouse model of transient middle cerebral artery occlusion/reperfusion. We found that IFNβ not only reduced infarct size in ischemic brains but also lessened neurological deficits in ischemic stroke animals. Further, multiple molecular mechanisms by which IFNβ modulates ischemic brain inflammation were identified. IFNβ reduced central nervous system infiltration of monocytes/macrophages, neutrophils, CD4(+) T cells, and γδ T cells; inhibited the production of inflammatory mediators; suppressed the expression of adhesion molecules on brain endothelial cells; and repressed microglia activation in the ischemic brain.

CONCLUSIONS

Our results demonstrate that IFNβ exerts a protective effect against ischemic stroke through its anti-inflammatory properties and suggest that IFNβ is a potential therapeutic agent, targeting the reperfusion damage subsequent to the treatment with tissue plasminogen activator.