Autoimmunity: Interferon α or β: which is the culprit in autoimmune disease?

Autoimmune liver disease and multiple sclerosis: state of the art and future perspectives

Clinical observations suggest that the prevalence of autoimmune diseases is changing over time. Both autoimmune liver diseases and multiple sclerosis have shown a significant increase in the last decades. Although the coexistence of autoimmune diseases within individuals and families is a common phenomenon, the extent to which liver disease and multiple sclerosis co-occur is not clear. Case reports and few studies have reported the possible coexistence of multiple sclerosis with thyroid diseases, inflammatory bowel disease, psoriasis, and rheumatoid arthritis. It is unknown whether there is a definite association between multiple sclerosis and autoimmune liver diseases. We reviewed the literature to summarize the available studies on the association between different autoimmune liver diseases (autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis) and treated or untreated multiple sclerosis.

Spatial enrichment of the type 1 interferon signature in the brain of a neuropsychiatric lupus murine model

Among systemic lupus erythematosus (SLE) patients, neuropsychiatric symptoms are highly prevalent, being observed in up to 80% of adult and 95% of pediatric patients. Type 1 interferons, particularly interferon alpha (IFNα), have been implicated in the pathogenesis of SLE and its associated neuropsychiatric symptoms (NPSLE). However, it remains unclear how type 1 interferon signaling in the central nervous system (CNS) might result in neuropsychiatric sequelae. In this study, we validate an NPSLE mouse model and find an elevated peripheral type 1 interferon signature alongside clinically relevant NPSLE symptoms such as anxiety and fatigue. Unbiased single-nucleus sequencing of the hindbrain and hippocampus revealed that interferon-stimulated genes (ISGs) were among the most highly upregulated genes in both regions and that gene pathways involved in cellular interaction and neuronal development were generally repressed among astrocytes, oligodendrocytes, and neurons. Using image-based spatial transcriptomics, we found that the type 1 interferon signature is enriched as spatially distinct patches within the brain parenchyma of these mice. Our results suggest that type 1 interferon in the CNS may play an important mechanistic role in mediating NPSLE behavioral phenotypes by repressing general cellular communication pathways, and that type 1 interferon signaling modulators are a potential therapeutic option for NPSLE.

[WITHDRAWN] Spatial enrichment of the type 1 interferon signature in the brain of a neuropsychiatric lupus murine model

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Pathogenic cellular and molecular mediators in lupus nephritis

Kidney involvement in patients with systemic lupus erythematosus - lupus nephritis (LN) - is one of the most important and common clinical manifestations of this disease and occurs in 40-60% of patients. Current treatment regimens achieve a complete kidney response in only a minority of affected individuals, and 10-15% of patients with LN develop kidney failure, with its attendant morbidity and considerable prognostic implications. Moreover, the medications most often used to treat LN - corticosteroids in combination with immunosuppressive or cytotoxic drugs - are associated with substantial side effects. Advances in proteomics, flow cytometry and RNA sequencing have led to important new insights into immune cells, molecules and mechanistic pathways that are instrumental in the pathogenesis of LN. These insights, together with a renewed focus on the study of human LN kidney tissue, suggest new therapeutic targets that are already being tested in lupus animal models and early-phase clinical trials and, as such, are hoped to eventually lead to meaningful improvements in the care of patients with systemic lupus erythematosus-associated kidney disease.

AllerCatPro 2.0: a web server for predicting protein allergenicity potential

Proteins in food and personal care products can pose a risk for an immediate immunoglobulin E (IgE)-mediated allergic response. Bioinformatic tools can assist to predict and investigate the allergenic potential of proteins. Here we present AllerCatPro 2.0, a web server that can be used to predict protein allergenicity potential with better accuracy than other computational methods and new features that help assessors making informed decisions. AllerCatPro 2.0 predicts the similarity between input proteins using both their amino acid sequences and predicted 3D structures towards the most comprehensive datasets of reliable proteins associated with allergenicity. These datasets currently include 4979 protein allergens, 162 low allergenic proteins, and 165 autoimmune allergens with manual expert curation from the databases of WHO/International Union of Immunological Societies (IUIS), Comprehensive Protein Allergen Resource (COMPARE), Food Allergy Research and Resource Program (FARRP), UniProtKB and Allergome. Various examples of profilins, autoimmune allergens, low allergenic proteins, very large proteins, and nucleotide input sequences showcase the utility of AllerCatPro 2.0 for predicting protein allergenicity potential. The AllerCatPro 2.0 web server is freely accessible at https://allercatpro.bii.a-star.edu.sg.

The role of cyclic GMP-AMP synthase and Interferon-I-inducible protein 16 as candidatebiomarkers of systemic lupus erythematosus

BACKGROUND

Diverse clinical and serological manifestations of systemic lupus erythematosus (SLE) compromise its diagnosis and treatment. A more reliable biomarker for SLE, which can play a critical role in either diagnosis, monitoring the disease progress or evaluating the response to treatment for individualized therapeutic, is necessary. DNA sensor is an important mediator of inflammation in systemic autoimmune diseases. However, the potential role for DNA sensor as disease activity biomarkers for SLE remained obscure. We detected the aberrant activation of DNA sensors and the corresponding IFN-β response in SLE patients, and to evaluate their potential role as disease biomarkers for SLE.

METHODS

We quantified the expressions of IFN-I and DNA sensor, such as cGAS, IFI16, DDX41, DAI and their down-stream adaptor STING in PBMC derived from patients with SLE (n = 100), healthy controls (HCs) (n = 62) by real-time PCR. The relationships between the expression of cGAS or IFI16 and clinical features in SLE patients were investigated. ROC curve analysis was performed to examine the predictive value of cGAS and IFI16 in SLE diagnosis, disease activity monitoring, specific organ manifestation and therapeutic response. RNA interference-mediated depletion of IFI16 or cGAS was conducted to evaluate their impact on IFN-I response.

RESULTS

The expressions of cGAS and IFI16 were significantly higher in PBMC from SLE patients, closely correlated with the SLEDAI scores and high anti-dsDNA antibody titers. While the AUC for cGAS (0.767) was less than that of IFI16 and IFN-β, the AUC for IFI16 (0.856) and IFN-β (0.856) were similar. Expression of cGAS and IFI16 combine with IFN-β in PBMC showed high sensitivity (89.2%) and specificity (89.1%) for discrimination between mild and moderate/severe disease activity in SLE. Higher expression of IFI16 was association with ocular disorder in SLE patients. Neither IFI16 nor cGAS was a reliable indicator of therapeutic response. RNA interference-mediated depletion of IFI16 or cGAS prevented active SLE serum-induced upregulating in both IFN-α and IFN-β.

CONCLUSIONS

High expression levels of cGAS and IFI16 in PBMC from SLE patients correlated strongly with disease activity. Both cGAS and IFI16 mediated signaling pathway were account for the robust production of IFN-β. Expression of cGAS and IFI16 combined with IFN-β in PBMC might serve as potential biomarkers for early diagnosis and monitoring disease activity in SLE.

What's the deal with efferocytosis and asthma?

Mucosal sites, such as the lung, serve as crucial, yet vulnerable barriers to environmental insults such as pathogens, allergens, and toxins. Often, these exposures induce massive infiltration and death of short-lived immune cells in the lung, and efficient clearance of these cells is important for preventing hyperinflammation and resolving immunopathology. Herein, we review recent advances in our understanding of efferocytosis, a process whereby phagocytes clear dead cells in a noninflammatory manner. We further discuss how efferocytosis impacts the onset and severity of asthma in humans and mammalian animal models of disease. Finally, we explore how recently identified genetic perturbations or biological pathway modulations affect pathogenesis and shed light on novel therapies aimed at treating or preventing asthma.

JAK inhibitors: a potential treatment for JDM in the context of the role of interferon-driven pathology

Juvenile Idiopathic Inflammatory Myopathies (IIM) are a group of rare diseases that are heterogeneous in terms of pathology that can include proximal muscle weakness, associated skin changes and systemic involvement. Despite options for treatment, many patients continue to suffer resistant disease and lasting side-effects. Advances in the understanding of the immunopathology and genetics underlying IIM may specify new therapeutic targets, particularly where conventional treatment has not achieved a clinical response. An upregulated type I interferon signature is strongly associated with disease and could be a prime target for developing more specific therapeutics. There are multiple components of the IFN pathway that could be targeted for blockade therapy.Downstream of the cytokine receptor complexes are the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway, which consists of JAK1-3, TYK2, and STAT1-6. Therapeutic inhibitors have been developed to target components of this pathway. Promising results have been observed in case studies reporting the use of the JAK inhibitors, Baricitinib, Tofacitinib and Ruxolitinib in the treatment of refractory Juvenile Dermatomyositis (JDM). There is still the question of safety and efficacy for the use of JAK inhibitors in JDM that need to be addressed by clinical trials. Here we review the future for the use of JAK inhibitors as a treatment for JDM.

Systemic lupus erythematosus (SLE): emerging therapeutic targets

INTRODUCTION

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a heterogeneous clinical presentation whose etiologies are multifactorial. A myriad of genetic, hormonal, immunologic, and environmental factors contribute to its pathogenesis, and its diverse biological basis and phenotypic presentations make development of therapeutics difficult. In the past decade, tens of therapeutic targets with hundreds of individual candidate therapeutics have been investigated.

AREAS COVERED

We used a PUBMED database search through April 2020 to review the relevant literature. This review discusses therapeutic targets in the adaptive and innate immune systems, specifically: B cell surface antigens, B cell survival factors, Bruton's tyrosine kinase, costimulators, IL-12/IL-23, the calcineurin pathway, the JAK/STAT pathway, and interferons.

EXPERT OPINION

Our ever-improving understanding of SLE pathophysiology in the past decade has allowed us to identify new therapeutic targets. Multiple new drugs are on the horizon that target different elements of the adaptive and innate immune systems. SLE research remains challenging due to the heterogenous clinical presentation of SLE, confounding from background immunosuppressives being taken by SLE patients, animal models that inadequately recapitulate human disease, and imperfect and complicated outcome measures. Despite these limitations, research is promising and ongoing. The search for new therapies that target specific elements of SLE pathophysiology are discussed as well as key findings, pitfalls, and questions surrounding these targets.

Cell-cycle-gated feedback control mediates desensitization to interferon stimulation

Cells use molecular circuits to interpret and respond to extracellular cues, such as hormones and cytokines, which are often released in a temporally varying fashion. In this study, we combine microfluidics, time-lapse microscopy, and computational modeling to investigate how the type I interferon (IFN)-responsive regulatory network operates in single human cells to process repetitive IFN stimulation. We found that IFN-α pretreatments lead to opposite effects, priming versus desensitization, depending on input durations. These effects are governed by a regulatory network composed of a fast-acting positive feedback loop and a delayed negative feedback loop, mediated by upregulation of ubiquitin-specific peptidase 18 (USP18). We further revealed that USP18 upregulation can only be initiated at the G1/early S phases of cell cycle upon the treatment onset, resulting in heterogeneous and delayed induction kinetics in single cells. This cell cycle gating provides a temporal compartmentalization of feedback loops, enabling duration-dependent desensitization to repetitive stimulations.

Established and Emerging Immunological Complications of Biological Therapeutics in Multiple Sclerosis

Biologic immunotherapies have transformed the treatment landscape of multiple sclerosis. Such therapies include recombinant proteins (interferon beta), as well as monoclonal antibodies (natalizumab, alemtuzumab, daclizumab, rituximab and ocrelizumab). Monoclonal antibodies show particular efficacy in the treatment of the inflammatory phase of multiple sclerosis. However, the immunological perturbations caused by biologic therapies are associated with significant immunological adverse reactions. These include development of neutralising immunogenicity, secondary immunodeficiency and secondary autoimmunity. These complications can affect the balance of risks and benefits of biologic agents, and 2018 saw the withdrawal from the market of daclizumab, an anti-CD25 monoclonal antibody, due to concerns about the development of severe, unpredictable autoimmunity. Here we review established and emerging risks associated with multiple sclerosis biologic agents, with an emphasis on their immunological adverse effects. We also discuss the specific challenges that multiple sclerosis biologics pose to drug safety systems, and the potential for improvements in safety frameworks.

Autoreactive B cells in SLE, villains or innocent bystanders?

The current concepts for development of autoreactive B cells in SLE (systemic lupus erythematosus) focus on extrinsic stimuli and factors that provoke B cells into tolerance loss. Traditionally, major tolerance loss pathways are thought to be regulated by factors outside the B cell including autoantigen engagement of the B-cell receptor (BCR) with simultaneous type I interferon (IFN) produced by dendritic cells, especially plasmacytoid dendritic cells (pDCs). Later, in autoreactive follicles, B-cells encounter T-follicular helper cells (Tfh) that produce interleukin (IL)-21, IL-4 and pathogenic cytokines, IL-17 and IFN gamma (IFNɣ). This review discusses these mechanisms and also highlights recent advances pointing to the peripheral transitional B-cell stage as a major juncture where transient autocrine IFNβ expression by developing B-cells imprints a heightened susceptibility to external factors favoring differentiation into autoantibody-producing plasmablasts. Recent studies highlight transitional B-cell heterogeneity as a determinant of intrinsic resistance or susceptibility to tolerance loss through the shaping of B-cell responsiveness to cytokines and other environment factors.

Matrix Metalloproteases as Influencers of the Cells' Social Media

Matrix metalloproteinases (MMPs) have been studied in the context of cancer due to their ability to increase cell invasion, and were initially thought to facilitate metastasis solely through the degradation of the extracellular matrix (ECM). MMPs have also been investigated in the context of their ECM remodeling activity in several acute and chronic inflammatory diseases. However, after several MMP inhibitors failed in phase III clinical trials, a global reassessment of their biological functions was undertaken, which has revealed multiple unanticipated functions including the processing of chemokines, cytokines, and cell surface receptors. Despite what their name suggests, the matrix aspect of MMPs could contribute to a lesser part of their physiological functions in inflammatory diseases, as originally anticipated. Here, we present examples of MMP substrates implicated in cell signaling, independent of their ECM functions, and discuss the impact for the use of MMP inhibitors.

Matrix metalloproteinases in the CNS: interferons get nervous

Matrix metalloproteinases (MMPs) have been investigated in context of chronic inflammatory diseases and demonstrated to degrade multiple components of the extracellular matrix (ECM). However, following several disappointing MMP clinical trials, recent studies have demonstrated unexpected novel functions of MMPs in viral infections and autoimmune inflammatory diseases in unanticipated locations. Thus, MMPs play additional functions in inflammation than just ECM degradation. They can regulate the activity of chemokines and cytokines of the immune response by precise proteolytic processing resulting in activation or inactivation of signaling pathways. MMPs have been demonstrated to cleave multiple substrates of the central nervous systems (CNS) and contribute to promoting and dampening diseases of the CNS. Initially, believed to be solely promoting pathologies, more than 10 MMPs to date have been shown to have protective functions. Here, we present some of the beneficial and destructive roles of MMPs in CNS pathologies and discuss strategies for the use of MMP inhibitors.

Interferon (IFN)-inducible Absent in Melanoma 2 proteins in the negative regulation of the type I IFN response: Implications for lupus nephritis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that exhibits a strong female bias (female-to-male ratio 9:1) in patients. Further, 40-60% SLE patients develop lupus nephritis (LN), which significantly increases the mortality rates. The failure of current therapies to adequately treat LN in patients reflects an incomplete understanding of the disease pathogenesis. Notably, a chronic increase in serum interferon-α (IFN-α) activity is a heritable risk factor to develop SLE. Accordingly, blood cells from most SLE patients with an active disease exhibit an increase in the expression of the type I IFN (IFN-α/β)-stimulated genes (ISGs, also referred to as "IFN-signature"), a type I IFN response. Further, LN patients during renal flares also exhibit an "IFN-signature" in renal biopsies. Therefore, an improved understanding of the regulation of type I IFNs expression is needed. Basal levels of the IFN-β through "priming" of IFN-α producing cells augment the expression of the IFN-α genes. Of interest, recent studies have indicated a role for the type I IFN-inducible Absent in Melanoma 2 proteins (the murine Aim2 and human AIM2) in the negative regulation of the type I IFN response through inflammasome-dependent and independent mechanisms. Further, an increase in the expression of Aim2 and AIM2 proteins in kidney and renal macrophages associated with the development of nephritis. Therefore, we discuss the role of Aim2/AIM2 proteins in the regulation of type I IFNs and LN. An improved understanding of the mechanisms by which the Absent in Melanoma 2 proteins suppress the type I IFN response and modulate nephritis is key to identify novel therapeutic targets to treat a group of LN patients.

Oligoadenylate-Synthetase-Family Protein OASL Inhibits Activity of the DNA Sensor cGAS during DNA Virus Infection to Limit Interferon Production

Interferon-inducible human oligoadenylate synthetase-like (OASL) and its mouse ortholog, Oasl2, enhance RNA-sensor RIG-I-mediated type I interferon (IFN) induction and inhibit RNA virus replication. Here, we show that OASL and Oasl2 have the opposite effect in the context of DNA virus infection. In Oasl2^-/- mice and OASL-deficient human cells, DNA viruses such as vaccinia, herpes simplex, and adenovirus induced increased IFN production, which resulted in reduced virus replication and pathology. Correspondingly, ectopic expression of OASL in human cells inhibited IFN induction through the cGAS-STING DNA-sensing pathway. cGAS was necessary for the reduced DNA virus replication observed in OASL-deficient cells. OASL directly and specifically bound to cGAS independently of double-stranded DNA, resulting in a non-competitive inhibition of the second messenger cyclic GMP-AMP production. Our findings define distinct mechanisms by which OASL differentially regulates host IFN responses during RNA and DNA virus infection and identify OASL as a negative-feedback regulator of cGAS.

Association of Abnormal Elevations in IFIT3 With Overactive Cyclic GMP-AMP Synthase/Stimulator of Interferon Genes Signaling in Human Systemic Lupus Erythematosus Monocytes

OBJECTIVE

Increasing evidence indicates that the cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) signaling pathway has a critical pathogenic role in systemic lupus erythematosus (SLE). Expression levels of the interferon (IFN)-inducible gene IFIT3 are elevated in SLE patients. However, it is still not clear how IFIT3 contributes to the pathogenesis of SLE. This study was undertaken to investigate the activation of the cGAS/STING signaling pathway in human SLE monocytes, and to determine how elevated expression of IFIT3 could contribute to overactive cGAS/STING signaling in patients with SLE.

METHODS

Monocytes from SLE patients or healthy controls were examined for activity of the cGAS/STING signaling pathway and expression levels of IFIT3. Correlations between cGAS/STING signaling activity and SLE clinical features were analyzed. Gain- or loss-of-function experiments were used to determine the role of IFIT3 in cGAS/STING signaling. Coimmunoprecipitation assays were used to identify the interaction between IFIT3 and other proteins.

RESULTS

The cGAS/STING signaling pathway was found to have enhanced activity in monocytes from SLE patients compared to healthy controls, as indicated by the higher expression of IFNβ downstream. Levels of IFIT3 were significantly elevated in human SLE monocytes, and this was positively correlated with the activity of the cGAS/STING signaling pathway. In vitro, the expression of VACV70-induced IFNβ was reduced by knockdown of IFIT3, whereas overexpression of IFIT3 produced an opposite effect. Finally, IFIT3 was found to interact with both STING and TANK-binding kinase 1.

CONCLUSION

These findings suggest that IFIT3 is one of the genes that contributes to the overactive cGAS/STING signaling pathway in human SLE monocytes. IFIT3 may therefore serve as a novel therapeutic target for blocking the production of type I IFN and other proinflammatory cytokines by the cGAS/STING signaling pathway in patients with SLE.

Cutting Edge: Intracellular IFN-β and Distinct Type I IFN Expression Patterns in Circulating Systemic Lupus Erythematosus B Cells

In systemic lupus erythematosus (SLE), type I IFNs promote induction of type I IFN-stimulated genes (ISG) and can drive B cells to produce autoantibodies. Little is known about the expression of distinct type I IFNs in lupus, particularly high-affinity IFN-β. Single-cell analyses of transitional B cells isolated from SLE patients revealed distinct B cell subpopulations, including type I IFN producers, IFN responders, and mixed IFN producer/responder clusters. Anti-Ig plus TLR3 stimulation of SLE B cells induced release of bioactive type I IFNs that could stimulate HEK-Blue cells. Increased levels of IFN-β were detected in circulating B cells from SLE patients compared with controls and were significantly higher in African American patients with renal disease and in patients with autoantibodies. Together, the results identify type I IFN-producing and -responding subpopulations within the SLE B cell compartment and suggest that some patients may benefit from specific targeting of IFN-β.

Interferon-stimulated genes: new platforms and computational approaches

Interferon-stimulated genes (ISGs) are the effectors of interferon (IFN) actions and play major roles in innate immune defense against microbial infection. During virus infection, ISGs impart antiviral actions to control virus replication and spread but can also contribute to disease pathology if their expression is unchecked. Antiviral ISGs have been identified by a variety of biochemical, genetic, and virologic methods. New computational approaches are expanding and redefining ISGs as responders to a variety of stimuli beyond IFNs, including virus infection, stress, and other events that induce cytokines. These studies reveal that the expression of ISG subsets link to interferon regulatory factors (IRF)s, NF-kB, and other transcription factors that impart gene expression in specific cell types independently of IFNs, including stem cells and other cell types where ISGs are constitutively expressed. Here, we provide a broad overview of ISGs, define virus-induced genes (VSG)s, and discuss the application of computational approaches and bioinformatics platforms to evaluate the functional role of ISGs in epigenetics, immune programming, and vaccine responses.

Genome-Wide DNA Methylation Analysis in Systemic Sclerosis Reveals Hypomethylation of IFN-Associated Genes in CD4+ and CD8+ T Cells

Epigenetic modifications, including DNA methylation, play an important role in the pathogenesis of autoimmune diseases. In this study, we characterized the DNA methylome in primary T cells of patients with systemic sclerosis. Genome-wide DNA methylation assays of CD4⁺ and CD8⁺ T cells from 24 systemic sclerosis patients and 24 matched controls were conducted and differentially methylated regions were validated. In the discovery stage, we found that hypomethylation of genes involved in the type I IFN signaling pathway was significantly enriched in both CD4⁺ (P = 7.59 × 10^-6) and CD8⁺ (P = 2.10 × 10^-8) differentially methylated regions. In the validation stage, we confirmed these changes for five type I IFN-associated genes. In addition, protein levels of both type I IFN-α (P < 0.0001) and β (P = 0.002) were significantly elevated in the sera of systemic sclerosis patients. Moreover, significant associations between type I IFN-α/β protein levels with the DNA methylation status as well as the expression profiles of these IFN-associated genes were confirmed. In conclusion, the type I IFN pathway is dysfunctional at the epigenetic level in systemic sclerosis patients, indicating that hypomethylation and upregulation of type I IFN-associated genes might be critical in systemic sclerosis pathogenesis.

Targeting interferons and their pathways in systemic lupus erythematosus

Significant advances in the understanding of the molecular basis of innate immunity have led to the identification of interferons (IFNs), particularly IFN-α, as central mediators in the pathogenesis of Systemic Lupus Erythematosus. Therefore, targeting of IFNs and of their downstream pathways has emerged as important developments for novel drug research in SLE. Based on this, several specific interferon blocking strategies using anti-IFN-α antibodies, anti-type I interferon receptor antibodies, Interferon-α-kinoid, or anti-IFN-γ antibodies have all been assessed in recent clinical trials. Alternative strategies targeting the plasmacytoid dendritic cells (pDCs), Toll-Like Receptors (TLRs)-7/9 or their downstream pathways such as the myeloid differentiation primary-response protein 88 (MYD88), spleen tyrosine kinase (Syk), Janus-kinases (JAKs), interleukin-1 receptor-associated kinase 4 (IRAK4), or the Tyrosine Kinase 2 (TYK2) are also investigated actively in SLE, at more preliminary clinical development stages, except for JAK inhibitors which have reached phase 2 studies. In a near future, in-depth and personalized functional characterization of IFN pathways may provide further guidance for the selection of the most relevant therapeutic strategy in SLE, tailored at the patient-level.

Interactions between Type 1 Interferons and the Th17 Response in Tuberculosis: Lessons Learned from Autoimmune Diseases

The classical paradigm of tuberculosis (TB) immunity, with a central protective role for Th1 responses and IFN-γ-stimulated cellular responses, has been challenged by unsatisfactory results of vaccine strategies aimed at enhancing Th1 immunity. Moreover, preclinical TB models have shown that increasing IFN-γ responses in the lungs is more damaging to the host than to the pathogen. Type 1 interferon signaling and altered Th17 responses have also been associated with active TB, but their functional roles in TB pathogenesis remain to be established. These two host responses have been studied in more detail in autoimmune diseases (AID) and show functional interactions that are of potential interest in TB immunity. In this review, we first identify the role of type 1 interferons and Th17 immunity in TB, followed by an overview of interactions between these responses observed in systemic AID. We discuss (i) the effects of GM-CSF-secreting Th17.1 cells and type 1 interferons on CCR2⁺ monocytes; (ii) convergence of IL-17 and type 1 interferon signaling on stimulating B-cell activating factor production and the central role of neutrophils in this process; and (iii) synergy between IL-17 and type 1 interferons in the generation and function of tertiary lymphoid structures and the associated follicular helper T-cell responses. Evaluation of these autoimmune-related pathways in TB pathogenesis provides a new perspective on recent developments in TB research.

Absent in Melanoma 2 proteins in SLE

Type I interferons (IFN-α/β)-inducible PYRIN and HIN domain-containing protein family includes Absent in Melanoma 2 (murine Aim2 and human AIM2), murine p202, and human PYRIN-only protein 3 (POP3). The generation of Aim2-deficient mice indicated that the Aim2 protein is essential for inflammasome activation, resulting in the secretion of interleukin-1β (IL-1β) and IL-18 and cell death by pyroptosis. Further, Aim2-deficiency also increased constitutive expression of the IFN-β and expression of the p202 protein. Notably, an increased expression of p202 protein in female mice associated with the development of systemic lupus erythematosus (SLE). SLE in patients is characterized by a constitutive increase in serum levels of IFN-α and an increase in the expression IFN-stimulated genes. Recent studies indicate that p202 and POP3 proteins inhibit activation of the Aim2/AIM2 inflammasome and promote IFN-β expression. Therefore, we discuss the role of Aim2/AIM2 proteins in the suppression of type I IFNs production and lupus susceptibility.