Multiple type I interferons and interferon-γ (IFN-γ) are expressed under physiological conditions and are increased by stress and infections, and in autoinflammatory and autoimmune diseases. ...Interferons activate the Jak-STAT signaling pathway and induce overlapping patterns of expression, called 'interferon signatures', of canonical interferon-stimulated genes (ISGs) encoding molecules important for antiviral responses, antigen presentation, autoimmunity and inflammation. It has now become clear that interferons also induce an 'interferon epigenomic signature' by activating latent enhancers and 'bookmarking' chromatin, thus reprogramming cell responses to environmental cues. The interferon epigenomic signature affects ISGs and other gene sets, including canonical targets of the transcription factor NF-κB that encode inflammatory molecules, and is involved in the priming of immune cells, tolerance and the training of innate immune memory. Here we review the mechanisms through which interferon signatures and interferon epigenomic signatures are generated, as well as the expression and functional consequences of these signatures in homeostasis and autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis and systemic sclerosis.
Following the discovery of plasmacytoid dendritic cells (pDCs) and of their extraordinary ability to produce type I IFNs (IFN-I) in response to TLR7 and TLR9 stimulation, it is assumed that their ...main function is to participate in the antiviral response. There is increasing evidence suggesting that pDCs and/or IFN-I can also have a detrimental role in a number of inflammatory and autoimmune diseases, in the context of chronic viral infections and in cancers. Whether these cells should be targeted in patients and how much of their biology is connected to IFN-I production remains unclear and is discussed here.
An important concept in immunology is the classification of immune responses as either innate or adaptive, based on whether the antigen receptors are encoded in the germline or generated somatically ...by gene rearrangement. The innate immune system is an ancient mode of immunity, and by being a first layer in our defense against infectious agents, it is essential for our ability to develop rapid and sustained responses to pathogens. We discuss the importance of nucleic acid recognition by the innate immune system to mounting an appropriate immune response to pathogens and also how inflammation driven by uncontrolled recognition of self-nucleic acids can lead to autoimmune diseases. We also summarize current efforts to either harness the immune system using agonists of nucleic acid-specific innate sensors or, on the contrary, by using inhibitors in autoimmune situations.
TLR8: No gain, no pain Barrat, Franck J
The Journal of experimental medicine,
12/2018, Letnik:
215, Številka:
12
Journal Article
Recenzirano
Odprti dostop
TLRs have been well characterized in the context of immunity, although TLR8 is understudied due to its controversial function in mice. In this issue of
, the new work by Zhang et al. ...(https://doi.org/10.1084/jem.20180800) demonstrates that TLR8 activated by miR-21 controls neuropathic pain using a non-MyD88-dependent pathway.
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by a breakdown of tolerance to nuclear antigens and the development of immune complexes. Genomic approaches have ...shown that human SLE leukocytes homogeneously express type I interferon (IFN)-induced and neutrophil-related transcripts. Increased production and/or bioavailability of IFN-α and associated alterations in dendritic cell (DC) homeostasis have been linked to lupus pathogenesis. Although neutrophils have long been shown to be associated with lupus, their potential role in disease pathogenesis remains elusive. Here, we show that mature SLE neutrophils are primed in vivo by type I IFN and die upon exposure to SLE-derived anti-ribonucleoprotein antibodies, releasing neutrophil extracellular traps (NETs). SLE NETs contain DNA as well as large amounts of LL37 and HMGB1, neutrophil proteins that facilitate the uptake and recognition of mammalian DNA by plasmacytoid DCs (pDCs). Indeed, SLE NETs activate pDCs to produce high levels of IFN-α in a DNA- and TLR9 (Toll-like receptor 9)-dependent manner. Our results reveal an unsuspected role for neutrophils in SLE pathogenesis and identify a novel link between nucleic acid-recognizing antibodies and type I IFN production in this disease.
Dendritic cell (DC) responses to extracellular self-DNA and self-RNA are prevented by the endosomal seclusion of nucleic acid-recognizing Toll-like receptors (TLRs). In psoriasis, however, ...plasmacytoid DCs (pDCs) sense self-DNA that is transported to endosomal TLR9 upon forming a complex with the antimicrobial peptide LL37. Whether LL37 also interacts with extracellular self-RNA and how this may contribute to DC activation in psoriasis is not known. Here, we report that LL37 can bind self-RNA released by dying cells, protect it from extracellular degradation, and transport it into endosomal compartments of DCs. In pDC, self-RNA-LL37 complexes activate TLR7 and, like self-DNA-LL37 complexes, trigger the secretion of IFN-alpha without inducing maturation or the production of IL-6 and TNF-alpha. In contrast to self-DNA-LL37 complexes, self-RNA-LL37 complexes also trigger the activation of classical myeloid DCs (mDCs). This occurs through TLR8 and leads to the production of TNF-alpha and IL-6, and the differentiation of mDCs into mature DCs. We also found that self-RNA-LL37 complexes are present in psoriatic skin lesions and are associated with mature mDCs in vivo. Our results demonstrate that the cationic antimicrobial peptide LL37 converts self-RNA into a trigger of TLR7 and TLR8 in human DCs, and provide new insights into the mechanism that drives the auto-inflammatory responses in psoriasis.
The identification of the antigen recognition receptors for innate immunity, most notably the Toll-like receptors, has sparked great interest in therapeutic manipulation of the innate immune system. ...Toll-like receptor agonists are being developed for the treatment of cancer, allergies and viral infections, and as adjuvants for potent new vaccines to prevent or treat cancer and infectious diseases. As recognition grows of the role of inappropriate Toll-like receptor stimulation in inflammation and autoimmunity, significant efforts have begun to develop antagonists to Toll-like receptors as well.
Interleukin-10 (IL-10) is a cytokine with broad anti-inflammatory properties by its suppression of both macrophage and dendritic cell function, including antigen-presenting cell function and the ...production of proinflammatory cytokines. This can result subsequently in the feedback regulation of both T-helper 1 (Th1)-type and Th2-type responses. This review discusses the potential use of IL-10 or agents that induce IL-10 as potential anti-inflammatory therapies in inflammatory diseases. Although IL-10-deficient mice develop colitis in the presence of normal gut flora and clear certain intracellular pathogens more efficiently, this is often accompanied by immunopathology, which can be lethal to the host. This reinforces the anti-inflammatory properties of IL-10, although it should be noted that as discussed below, IL-10 can also promote B-cell and other immune responses under particular settings. A penalty of its role to limit the immune and inflammatory responses to pathogens and prevent damage to the host is that high or dysregulated levels of IL-10 may result in chronic infection. Thus, antagonists of IL-10 show great potential as adjuvants in preventative or therapeutic vaccines against chronic infection or cancer. This article reviews basic published studies on IL-10, which may lead to potential uses of IL-10 or its antagonists in human disease.
Type 1 diabetes develops over many years and is characterized ultimately by the destruction of insulin-producing pancreatic beta cells by autoreactive T cells. Nonetheless, the role of innate cells ...in the initiation of this disease remains poorly understood. Here, we show that in young female nonobese diabetic mice, physiological beta cell death induces the recruitment and activation of B-1a cells, neutrophils and plasmacytoid dendritic cells (pDCs) to the pancreas. Activated B-1a cells secrete IgGs specific for double-stranded DNA. IgGs activate neutrophils to release DNA-binding cathelicidin-related antimicrobial peptide (CRAMP), which binds self DNA. Then, self DNA, DNA-specific IgG and CRAMP peptide activate pDCs through the Toll-like receptor 9-myeloid differentiation factor 88 pathway, leading to interferon-α production in pancreatic islets. We further demonstrate through the use of depleting treatments that B-1a cells, neutrophils and IFN-α-producing pDCs are required for the initiation of the diabetogenic T cell response and type 1 diabetes development. These findings reveal that an innate immune cell crosstalk takes place in the pancreas of young NOD mice and leads to the initiation of T1D.
The innate immune system is a critical element of protection from invading pathogens. The specific receptors that recognize various components of the pathogens trigger signals that result in the ...production of proinflammatory cytokines as well as the activation of antigen-presenting cells, which activate the adaptive immune system. The discovery of the Toll-like receptors (TLRs) as important components of pathogen recognition has brought new understanding of the key signaling molecules involves in innate immune activation. Interestingly, it appears that most TLRs can recognize self-ligands as well and that mechanisms are required to discriminate between self and non-self ligands. One of these mechanisms is the expression of all the nucleic acid-specific TLR in endosomal compartments and not on the cell surface. Inappropriate activation of TLRs by self-components can result in sterile inflammation or autoimmunity. For example, TLR7 and TLR9 activation by endogenous RNA and DNA, transported to the endosomes in the form of immune complexes or non-covalently associated with cationic peptides, could be an important mechanism involved in promoting diseases such as systemic lupus erythematosus and psoriasis. In this review, we discuss the rationale for self-recognition by TLR7 and TLR9 as an important part of the development of lupus and other autoimmune diseases. We describe novel inhibitors of these receptors and provide evidence to support their use as novel therapeutic agents for autoimmunity.
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