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Innate immune defense mechanisms against infection and cancer encompass the modulation of pattern recognition receptor (PRR)‐mediated inflammation, including upregulation of various transcription factors and the activation of pro‐inflammatory pathways important for immune surveillance. Dysfunction of PRRs‐mediated signaling has been implicated in cancer and autoimmune diseases, while the overactivation of PRRs‐driven responses during infection can lead to devastating consequences such as acute lung injury or sepsis. We used crystal structure‐based design to develop immunomodulatory lipopolysaccharide (LPS) mimetics targeting one of the ubiquitous PRRs, Toll‐like Receptor 4 (TLR4). Taking advantage of an exo‐anomeric conformation and specific molecular shape of synthetic nonreducing β,β‐diglucosamine, which was investigated by NMR, we developed two sets of lipid A mimicking glycolipids capable of either potently activating innate immune responses or inhibiting pro‐inflammatory signaling. Stereoselective 1,1′‐glycosylation towards fully orthogonally protected nonreducing GlcNβ(1↔1′)βGlcN followed by stepwise assembly of differently functionalised phosphorylated glycolipids provided biologically active molecules that were evaluated for their ability to trigger or to inhibit cellular innate immune responses. Two LPS mimetics, identified as potent TLR4‐specific inducers of the intracellular signaling pathways, serve as vaccine adjuvant‐ and immunotherapy candidates, while anionic glycolipids with TLR4‐inhibitory potential hold therapeutic promise for the management of acute or chronic inflammation. [ABSTRACT FROM AUTHOR]

Toll‐like receptors (TLRs) are inflammatory triggers and belong to a family of pattern recognition receptors (PRRs) that are central to the regulation of host protective adaptive immune responses. Activation of TLRs in innate immune myeloid cells directs lymphocytes to produce the most appropriate effector responses to eliminate infection and maintain homeostasis of the body's internal environment. Inappropriate TLR stimulation can lead to the development of general autoimmune diseases as well as chronic and acute inflammation, and even cancer. Therefore, TLRs are expected to be targets for therapeutic treatment of inflammation‐related diseases, autoimmune diseases, microbial infections, and human cancers. This review summarizes the recent discoveries in the molecular and structural biology of TLRs. The role of different TLR signaling pathways in inflammatory diseases, autoimmune diseases such as diabetes, cardiovascular diseases, respiratory diseases, digestive diseases, and even cancers (oral, gastric, breast, colorectal) is highlighted and summarizes new drugs and related clinical treatments in clinical trials, providing an overview of the potential and prospects of TLRs for the treatment of TLR‐related diseases. [ABSTRACT FROM AUTHOR]

During the replication of viral genomes, RNA viruses produce double‐stranded RNA (dsRNA), through the activity of their RNA‐dependent RNA polymerases (RdRps) as viral replication intermediates. Recognition of viral dsRNA by host pattern recognition receptors – such as retinoic acid‐induced gene‐I (RIG‐I)‐like receptors and Toll‐like receptor 3 – triggers the production of interferon (IFN)‐β via the activation of IFN regulatory factor (IRF)‐3. It has been proposed that, during the replication of viral genomes, each of RIG‐I and melanoma differentiation‐associated gene 5 (MDA5) form homodimers for the efficient activation of a downstream signalling pathway in host cells. We previously reported that, in the non‐neoplastic human hepatocyte line PH5CH8, the RdRp NS5B derived from hepatitis C virus (HCV) could induce IFN‐β expression by its RdRp activity without the actual replication of viral genomes. However, the exact mechanism by which HCV NS5B produced IFN‐β remained unknown. In the present study, we first showed that NS5B derived from another Flaviviridae family member, GB virus B (GBV‐B), also possessed the ability to induce IFN‐β in PH5CH8 cells. Similarly, HCV NS5B, but not its G317V mutant, which lacks RdRp activity, induced the dimerization of MDA5 and subsequently the activation of IRF‐3. Interestingly, immunofluorescence analysis showed that HCV NS5B produced dsRNA. Like HCV NS5B, GBV‐B NS5B also triggered the production of dsRNA and subsequently the dimerization of MDA5. Taken together, our results show that HCV NS5B triggers an MDA5‐mediated innate immune response by producing dsRNA without the replication of viral genomes in human hepatocytes. [ABSTRACT FROM AUTHOR]

Crustacean species are among the most valued seafood with socioeconomic and ecological implications in the global fisheries sector. Microbial infections to the farming stock due to continued expansion and aquaculture puts global crustacean production at risk. Understanding and reviewing the complex innate immune system of crustaceans would be pivotal in formulating informed decisions for the control and management of epidemic diseases, thus making the global crustacean aquaculture industry sustainable. Under the purview of innate immunity in crustaceans, pattern recognition receptors (PRRs) represent the sensors capable of discriminating non‐self pathogenic modules and invoking the activation of immune responses. The immunity to infections can be manifested at cellular (via phagocytosis, apoptosis, nodulation and encapsulation) and humoral (effected by prophenoloxidase cascade, lectins, antimicrobial proteins) levels leading to the elimination of pathogens or subversion of the pathogenic implications. In this review, we discuss the participatory role of 12 types of PRRs identified from crustacean species with an exhaustive focus on structural and functional specificities in binding to pathogens and possible execution of the immune activity. Moreover, we have elaborated on the PRRs‐associated or possible signalling cascades (Toll‐NFκB, IMD‐NFκB and JAK‐STAT) in crustacean species that could bridge our understanding of the resistance or susceptibility of the host to varied pathogenic infections thus providing clues to the regulatory mechanisms involved in pathogenesis of infectious diseases and mechanisms of immunity. [ABSTRACT FROM AUTHOR]

Innate immunity is the first line of defense against infections, which functions as a significant role in resisting pathogen invasion. Rapid immune response is initiated by pattern recognition receptors (PRRs) quickly distinguishing "self" and "non‐self." Upon evolutionarily conserved pathogen‐associated molecular pattern (PAMP) is recognized by PRRs, innate immune response against infection is triggered via an orchestration of molecular interaction, cytokines cascades, and immune cells. RIG‐I plays a critical role in type I interferon (IFN‐I) production by direct recognition of cytoplasmic double‐stranded viral RNA. However, the activation mechanism of RIG‐I is incompletely understood. In this study, we reported RNA‐binding protein ZFP36 as a positive regulator of RIG‐I‐mediated IFN‐I production. ZFP36 is a member of Zinc finger proteins (ZFPs) characterized by the zinc finger (ZnF) motif, which broadly involved gene transcription and signal transduction. However, its role in regulating antiviral innate immune signaling is still unclear. We found that ZFP36 associates with RIG‐I and potentiates the FN‐β production induced by SeV. Mechanistically, ZFP36 promotes K63‐linked polyubiquitination of RIG‐I, mostly at K154/K164/K172, thereby facilitating the activation of RIG‐I during infection. While the mutant ZFP36 (C118S/C162S) failed to increase polyubiquitination of RIG‐I and SeV induced FN‐β. Our findings collectively demonstrated that ZFP36 acts as a positive regulator in antiviral innate immunity by targeting RIG‐I for K63‐linked ubiquitination, thus improving our understanding of the activation mechanism of RIG‐I. [ABSTRACT FROM AUTHOR]

Maintaining homeostasis is central to organismal health. Deviation is detected by a variety of sensors that react to alarm signals arising from injury, infection, and other inflammatory triggers. One important element of this alarm system is the innate immune system, which recognizes pathogen‐/microbe‐ or damage‐associated molecular patterns via pattern recognition receptors localized in the cytosol or in membranes of innate immune cells such as macrophages, dendritic cells, and mast cells but also of T cells, B cells, and epithelial cells. Activation of the innate immune system results in inflammation and is a pre‐requisite for activation of the adaptive immune system. Another important element is represented by the unfolded protein response (UPR), a stress response of the endoplasmic reticulum. The UPR regulates proteostasis and also contributes to the course of inflammatory diseases such as cancer, diabetes, obesity, and neurodegenerative diseases. In addition, the UPR is instrumental in allergic contact dermatitis. This inflammatory skin disease, affecting 5–10% of the population, is caused by T cells recognizing low‐molecular weight organic chemicals and metal ions. In this mini‐review, we discuss the orchestration of inflammatory responses by the interplay of the innate immune system with cellular stress responses in allergic contact dermatitis, with a focus on the UPR. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) is a chronic infectious disease mainly caused by Mycobacterium tuberculosis (M. tuberculosis). The structures of polysaccharides and glycolipids at M. tuberculosis cell wall vary among different strains, which affect the physiology and pathogenesis of mycobacteria by activating or inhibiting innate and acquired immunity. Among them, some components such as lipomannan (LM) and lipoarabinomannan (LAM) activate innate immunity by recognizing some kinds of pattern recognition receptors (PRRs) like Toll‐like receptors, while other components like mannose‐capped lipoarabinomannan (ManLAM) could prevent innate immune responses by inhibiting the secretion of pro‐inflammatory cytokines and maturation of phagosomes. In addition, many glycolipids can activate natural killer T (NKT) cells and CD1‐restricted T cells to produce interferon‐γ (IFN‐γ). Furthermore, humoral immunity against cell wall components, such as antibodies against LAM, plays a role in immunity against M. tuberculosis infection. Cell wall polysaccharides and glycolipids of M. tuberculosis have potential applications as antigens and adjuvants for novel TB subunit vaccines. [ABSTRACT FROM AUTHOR]

The gastrointestinal tract of all animals, including insects, is colonized by a remarkable array of microorganisms which are referred to collectively as the gut microbiota. The hosts establish mutually beneficial interactions with the gut microbiota. However, the mechanisms shaping these interactions remain to be better understood. Here, we investigated the roles of Musca domestica peptidoglycan recognition protein SC (MdPGRP‐SC), a secreted pattern recognition receptor, in shaping the gut microbial community structure by using biochemical and high‐throughput sequencing approaches. The recombinant MdPGRP‐SC (rMdPGRP‐SC) could strongly bind various pathogen‐associated molecular patterns (PAMPs) including peptidoglycan, lipopolysaccharide and D‐galactose, and exhibited mild affinity to β‐1, 3‐glucan and D‐mannose. Meanwhile, rMdPGRP‐SC could also bind different kinds of microorganisms, including gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus), gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and yeast (Pichia pastoris). rMdPGRP‐SC also exhibited weak antibacterial activity against Bacillus subtilis. Knockdown of MdPGRP‐SC by RNAi reduced the persistence of ingested E. coli and a load of indigenous microbiota in the larval gut significantly. In addition, depleted MdPGRP‐SC also altered the gut microbiota composition and led to increased ratios of Gram‐negative bacteria. We hypothesize that MdPGRP‐SC is involved in maintaining gut homeostasis by modulating the immune intensity of the gut through multiple mechanisms, including degrading or neutralizing various PAMPs and selectively suppressing the growth of some bacteria. Considering the functional conservation of the peptidoglycan recognition protein (PGRP) family in insects, the catalytic PGRPs might be promising candidate targets not only for pest and vector control but also for the treatment of bacterial infection in insect farming. [ABSTRACT FROM AUTHOR]

Organization and functioning of immune system remain unevenly studied in different taxa of lophotrochozoan animals. We analyzed transcriptomic data on coelomocytes of the lugworm Arenicola marina (Linnaeus, 1758; Annelida, Polychaeta) to gain insights into the molecular mechanisms involved in polychaete immunity. Coelomocytes are specialized motile cells populating coelomic fluid of annelids, responsible for cellular defense reactions and providing humoral immune factors. The transcriptome was enriched with immune‐related transcripts by challenging the cells in vitro with lipopolysaccharides of Escherichia coli and Zymosan from Saccharomyces cerevisiae. Our analysis revealed a multifaceted and complex internal defense system of the lugworm. A. marina possesses orthologs of proto‐complement‐like factors: six thioester‐containing proteins, a complement‐like receptor, and a MASP‐related serine protease (MReM2). A. marina coelomocytes employ pattern‐recognition receptors to detect pathogens and regulate immune responses. Among them, there are 18 Toll‐like receptors and various putative lectin‐like proteins with evolutionary conserved and taxa‐specific domains. C‐type lectins and a novel family of Gal‐binding and CUB domains containing receptors were the most abundant in the transcriptome. The array of pore‐forming proteins in the coelomocytes was surprisingly reduced compared to that of other invertebrate species. We characterized a set of conserved proteins metabolizing reactive oxygen species and nitric oxide and expanded the arsenal of potential antimicrobial peptides. Phenoloxidase activity in immune cells of lugworm is mediated only by laccase enzyme. The described repertoire of immune‐associated molecules provides valuable candidates for further functional and comparative research on the immunity of annelids. Research highlights: Lugworm coelomocytic transcriptome was assembled de novo and made available to the community.Lugworm has a complex immune system with several species‐ and higher‐taxa‐specific hallmarks.Putative immune‐related repertoire comprises evolutionary conserved and rapidly evolving genes. [ABSTRACT FROM AUTHOR]

Summary: Heterodimeric complexes incorporating the lipase‐like proteins EDS1 with PAD4 or SAG101 are central hubs in plant innate immunity. EDS1 functions encompass signal relay from TIR domain‐containing intracellular NLR‐type immune receptors (TNLs) towards RPW8‐type helper NLRs (RNLs) and, in Arabidopsis thaliana, bolstering of signaling and resistance mediated by cell‐surface pattern recognition receptors (PRRs). Increasing evidence points to the activation of EDS1 complexes by small molecule binding.We used CRISPR/Cas‐generated mutant lines and agroinfiltration‐based complementation assays to interrogate functions of EDS1 complexes in Nicotiana benthamiana.We did not detect impaired PRR signaling in N. benthamiana lines deficient in EDS1 complexes or RNLs. Intriguingly, in assays monitoring functions of SlEDS1‐NbEDS1 complexes in N. benthamiana, mutations within the SlEDS1 catalytic triad could abolish or enhance TNL immunity. Furthermore, nuclear EDS1 accumulation was sufficient for N. benthamiana TNL (Roq1) immunity.Reinforcing PRR signaling in Arabidopsis might be a derived function of the TNL/EDS1 immune sector. Although Solanaceae EDS1 functionally depends on catalytic triad residues in some contexts, our data do not support binding of a TNL‐derived small molecule in the triad environment. Whether and how nuclear EDS1 activity connects to membrane pore‐forming RNLs remains unknown. [ABSTRACT FROM AUTHOR]

Extensive crosstalk exists between autophagy and innate immune signalling pathways. The stimuli that induce pattern recognition receptor (PRR)‐mediated innate immune signalling pathways, also upregulate autophagy. The purpose of this increased autophagy is to eliminate the stimuli and/or suppress the inflammatory pathways by targeted degradation of PRRs or intermediary proteins (termed 'inflammophagy'). By executing these functions, autophagy dampens excess inflammation triggered by the innate immune signalling pathways. Thus, autophagy helps in the maintenance of the body's innate immune homeostasis to protect from inflammatory and autoimmune diseases. Many autophagy‐dependent mechanisms that could control innate immune signalling have been studied over the last few years. However, still, the understanding is incomplete, and studies that are more systematic should be undertaken to delineate the mechanisms of inflammophagy. Here, we discuss the available knowledge of crosstalk between autophagy and PRR signalling pathways. [ABSTRACT FROM AUTHOR]

As important pattern recognition receptors (PRRs), C‐type lectins play crucial roles in the crustacean innate immune system. In this study, a novel C‐type lectin, designated as MnLec1, was obtained from the exoskeleton of the oriental river prawn Macrobrachium nipponense for the first time. The full‐length cDNA of MnLec1 was 1329 bp with an open reading frame of 774 bp. The predicted MnLec1 protein contains a single carbohydrate‐recognition domain with an EPN/LND motif and one Ca2+ binding site‐2. MnLec1 transcripts were widely detected in the tested tissues of M. nipponense and significantly up‐regulated after Aeromonas hydrophila challenge. The recombinant MnLec1 protein was found to have a wide spectrum of binding activities towards various microorganisms, agglutinate two kinds of Gram‐negative bacteria (Escherichia coli and A. hydrophila) in a Ca2+‐independent manner. What's more, the survivability of prawns was significantly down‐regulated after RNAi of MnLec1 when infected with A. hydrophila. Collectively, these findings suggest that MnLec1 from the exoskeleton might function as a PRR and play a crucial role in immune defense against invading pathogens in M. nipponense. [ABSTRACT FROM AUTHOR]

RIG‐I is our first line of defense against RNA viruses, serving as a pattern recognition receptor that identifies molecular features common among dsRNA and ssRNA viral pathogens. RIG‐I is maintained in an inactive conformation as it samples the cellular space for pathogenic RNAs. Upon encounter with the triphosphorylated terminus of blunt‐ended viral RNA duplexes, the receptor changes conformation and releases a pair of signaling domains (CARDs) that are selectively modified and interact with an adapter protein (MAVS), thereby triggering a signaling cascade that stimulates transcription of interferons. Here, we describe the structural determinants for specific RIG‐I activation by viral RNA, and we describe the strategies by which RIG‐I remains inactivated in the presence of host RNAs. From the initial RNA triggering event to the final stages of interferon expression, we describe the experimental evidence underpinning our working knowledge of RIG‐I signaling. We draw parallels with behavior of related proteins MDA5 and LGP2, describing evolutionary implications of their collective surveillance of the cell. We conclude by describing the cell biology and immunological investigations that will be needed to accurately describe the role of RIG‐I in innate immunity and to provide the necessary foundation for pharmacological manipulation of this important receptor. [ABSTRACT FROM AUTHOR]

In their never‐ending quest towards persistence within their host, hepatitis viruses have developed numerous ways to counteract the liver innate immunity. This review highlights the different and common mechanisms employed by these viruses to (i) establish in the liver (passive entry or active evasion from immune recognition) and (ii) actively inhibit the innate immune response (ie modulation of pattern recognition receptor expression and/or signalling pathways, modulation of interferon response and modulation of immune cells count or phenotype). [ABSTRACT FROM AUTHOR]

Virus invasion activates the host's innate immune response, inducing the production of numerous cytokines and interferons to eliminate pathogens. Except for viral DNA/RNA, viral proteins are also targets of pattern recognition receptors. Membrane‐bound receptors such as Toll‐like receptor (TLR)1, TLR2, TLR4, TLR6, and TLR10 relate to the recognition of viral proteins. Distinct TLRs perform both protective and detrimental roles for a specific virus. Here, we review viral proteins serving as pathogen‐associated molecular patterns and their corresponding TLRs. These viruses are all enveloped, including respiratory syncytial virus, hepatitis C virus, measles virus, herpesvirus human immunodeficiency virus, and coronavirus, and can encode proteins to activate innate immunity in a TLR‐dependent way. The TLR‐viral protein relationship plays an important role in innate immunity activation. A detailed understanding of their pathways contributes to a novel direction for vaccine development. Highlights: 1. The TLR‐viral protein relationship plays an important role in innate immunity activation2. we review viral proteins serving as pathogen‐associated molecular patterns and their corresponding TLRs.3. Respiratory syncytial virus, hepatitis C virus, measles virus, herpesvirus human immunodeficiency virus, and coronavirus, and can encode proteins to activate innate immunity in a TLR‐dependent way. [ABSTRACT FROM AUTHOR]

Cytosolic DNA receptor cyclic GMP‐AMP (cGAMP) synthase (cGAS) has been shown to be critically involved in the detection of cytosolic, self‐ and non‐self‐DNA, initiating a type I IFN response through the adaptor protein Stimulator of Interferon Genes (STING) and interferon regulatory factor 3 (IRF3). Current studies propose that canonical binding of dsDNA by cGAS depends on DNA length, but not on base sequence. In contrast, activation of TLR9 is sequence dependent. It requires unmethylated CpG dinucleotides in microbial DNA, which is mimicked by synthetic oligodeoxynucleotides (ODN). Here, we provide evidence that d‐type ODN (D‐ODN), but not K‐type ODN (K‐ODN), bind to human cGAS and activate downstream signaling. Transfection of D‐ODN into a TLR9‐deficient, human monocytic cell line (THP‐1) induced phosphorylation of IRF3 and secretion of IFN. This response was absent in cells with CRISPR/Cas9‐mediated cGAS‐ or STING‐deficiency. Utilizing a protein pulldown approach, we further demonstrate direct binding of D‐ODN to cGAS. Induction of a type I IFN response by D‐ODN was confirmed in human primary monocytes and monocyte‐derived macrophages. These results are relevant to our understanding of self–nonself‐discrimination by cGAS and to the pharmacologic effects of ODN, which currently are investigated in clinical studies. [ABSTRACT FROM AUTHOR]

Gram‐positive bacteria ubiquitously produce membrane vesicles (MVs), and although they contribute to biological functions, our knowledge regarding their composition and immunogenicity remains limited. Here we examine the morphology, contents and immunostimulatory functions of MVs produced by three Staphylococcus aureus strains; a methicillin resistant clinical isolate, a methicillin sensitive clinical isolate and a laboratory‐adapted strain. We observed differences in the number and morphology of MVs produced by each strain and showed that they contain microbe‐associated molecular patterns (MAMPs) including protein, nucleic acids and peptidoglycan. Analysis of MV‐derived RNA indicated the presence of small RNA (sRNA). Furthermore, we detected variability in the amount and composition of protein, nucleic acid and peptidoglycan cargo carried by MVs from each S. aureus strain. S. aureus MVs activated Toll‐like receptor (TLR) 2, 7, 8, 9 and nucleotide‐binding oligomerization domain containing protein 2 (NOD2) signalling and promoted cytokine and chemokine release by epithelial cells, thus identifying that MV‐associated MAMPs including DNA, RNA and peptidoglycan are detected by pattern recognition receptors (PRRs). Moreover, S. aureus MVs induced the formation of and colocalized with autophagosomes in epithelial cells, while inhibition of lysosomal acidification using bafilomycin A1 resulted in accumulation of autophagosomal puncta that colocalized with MVs, revealing the ability of the host to degrade MVs via autophagy. This study reveals the ability of DNA, RNA and peptidoglycan associated with MVs to activate PRRs in host epithelial cells, and their intracellular degradation via autophagy. These findings advance our understanding of the immunostimulatory roles of Gram‐positive bacterial MVs in mediating pathogenesis, and their intracellular fate within the host. [ABSTRACT FROM AUTHOR]

C‐type lectins are carbohydrate‐binding proteins that play important roles in immunity by serving as pattern recognition receptors. In the present study, a novel nattectin‐like C‐type lectin was obtained from the weather loach, Misgurnus anguillicaudatus, designated as MaCTL. MaCTL encodes a peptide with 165 amino acids, with a signal peptide and a single C‐type lectin domain (CTLD), containing a galactose‐specific QPD motif and a conserved Ca2+‐binding site. Transcripts of MaCTL were significantly upregulated after immune challenge with its pathogen A. hydrophila. In vitro assays with recombinant MaCTL protein revealed that it exhibited hemagglutinating and bacterial agglutinating activities, in a Ca2+‐dependent manner. MaCTL was found to bind to a wide range of bacteria, as well as bind to bacterial polysaccharides LPS and PGN. Moreover, MaCTL displayed antimicrobial activity by inhibiting the growth of bacteria. These results collectively suggest that MaCTL is involved in the antibacterial defence of weather loach. [ABSTRACT FROM AUTHOR]

The migratory plant‐parasitic nematode Bursaphelenchus xylophilus is the causal agent of pine wilt disease, which causes serious damage to pine forests in China. Plant immunity plays an important role in plant resistance to multiple pathogens. Activation of the plant immune system is generally determined by immune receptors, including plant pattern recognition receptors, which mediate pattern recognition. However, little is known about molecular pattern recognition in the interaction between pines and B. xylophilus. Based on the B. xylophilus transcriptome at the early stages of infection and Agrobacterium tumefaciens‐mediated transient expression and infiltration of recombinant proteins produced by Pichia pastoris in many plant species, a novel molecular pattern (BxCDP1) was characterized in B. xylophilus. We found that BxCDP1 was highly up‐regulated at the early infection stages of B. xylophilus, and was similar to a protein in Pararhizobium haloflavum. BxCDP1 triggered cell death in Nicotiana benthamiana when secreted into the apoplast, and this effect was dependent on brassinosteroid‐insensitive 1‐associated kinase 1, but independent of suppressor of BIR1‐1. BxCDP1 also exhibited cell death‐inducing activity in pine, Arabidopsis, tomato, pepper, and lettuce. BxCDP1 triggered reactive oxygen species production and the expression of PAMP‐triggered immunity marker genes (NbAcre31, NbPTI5, and NbCyp71D20) in N. benthamiana. It also induced the expression of pathogenesis‐related genes (PtPR‐3, PtPR‐4, and PtPR‐5) in Pinus thunbergii. These results suggest that as a new B. xylophilus molecular pattern, BxCDP1 can not only be recognized by many plant species, but also triggers innate immunity in N. benthamiana and defence responses of P. thunbergii. [ABSTRACT FROM AUTHOR]

Background & Aims: Acute‐on‐chronic liver failure (ACLF) is characterized by acute decompensation of cirrhosis (AD), organ failure(s) and high risk of short‐term mortality with bacterial infection frequently as precipitating event. Innate immune pattern recognition receptors and members of the lectin pathway of complement activation are crucial to the innate immune response to pathogens. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) of innate immune components are associated with the occurrence of bacterial infections or mortality in patients with cirrhosis hospitalized for AD or ACLF. Methods: Twenty‐one innate immunity SNPs with known functional implications were genotyped in 826 AD/ACLF patients included in the CANONIC study. Associations between baseline characteristics of the patients, the occurrence of bacterial infections and survival rate at 90 days of follow‐up in relation to the innate immunity genetic variants were analysed. Results: The NOD2‐G908R genetic variant was associated with mortality (HR 2.25, P =.004) independently of age and MELD Score. This association was also found in a predefined subgroup analysis in patients with bacterial infections (HR 2.78, P <.001) along with MBL_Yx (HR 1.72, P =.008) and MASP2_371 (HR 1.67, P =.012) genetic variants. None of the analysed SNPs were significantly associated with the occurrence of acute bacterial infections or spontaneous bacterial peritonitis in particular. Conclusions: Innate immune system‐specific NOD2‐G908R, MBL_Yx and MASP2_371 genetic variants were independently associated with increased risk of short‐term mortality in AD/ACLF patients with bacterial infection. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore this relationship in the first year following severe exacerbation in our previously cited cohort of school-aged children.[7] We also compared asthma characteristics recorded at baseline and asthma outcomes at 1 year. At 1-year visit, patients were classified into three groups according to asthma outcomes: (a) good responders: no exacerbation during follow-up and well-controlled asthma according to GINA guidelines; (b) partial responders: no more than one severe exacerbation during follow-up and/or partly controlled asthma; (c) poor responders: >=2 severe exacerbations during follow-up and/or uncontrolled asthma. We also observed that control and lung function evaluated 8 weeks after an asthma exacerbation might be predictive of future asthma outcomes. The influence of asthma control on the severity of virus-induced asthma exacerbations. [Extracted from the article]

Plant pattern recognition receptors (PRRs) perceive pathogen‐associated molecular patterns (PAMPs) to activate immune responses. Medium‐chain 3‐hydroxy fatty acids (mc‐3‐OH‐FAs), which are widely present in Gram‐negative bacteria, were recently shown to be novel PAMPs in Arabidopsis thaliana. The Arabidopsis PRR LIPOOLIGOSACCHARIDE‐SPECIFIC REDUCED ELICITATION (LORE) is a G‐type lectin receptor‐like kinase that recognizes mc‐3‐OH‐FAs and subsequently mounts an immune response; however, the mechanisms underlying LORE activation and downstream signaling are unexplored. Here, we report that one of the mc‐3‐OH‐FAs, 3‐OH‐C10:0, induces phosphorylation of LORE at tyrosine residue 600 (Y600). Phosphorylated LORE subsequently trans‐phosphorylates the receptor‐like cytoplasmic kinase PBL34 and its close paralogs, PBL35 and PBL36, and therefore activates plant immunity. Phosphorylation of LORE Y600 is required for downstream phosphorylation of PBL34, PBL35, and PBL36. However, the Pseudomonas syringae effector HopAO1 targets LORE, dephosphorylating the tyrosine‐phosphorylated Y600 and therefore suppressing the immune response. These observations uncover the mechanism by which LORE mediates signaling in response to 3‐OH‐C10:0 in Arabidopsis. Synopsis: The Arabidopsis lectin receptor‐like kinase LORE serves as pattern‐recognition receptor for bacterial fatty acid metabolites. Here, LORE‐mediated activation of plant immune responses is shown to be mediated by LORE auto‐phosphorylation and activation of novel receptor‐like cytoplasmic kinases. LORE exhibits tyrosine kinase activity.Bacterial fatty acid metabolite 3‐OH‐C10:0 activates LORE via its phosphorylation on Tyr600.LORE phosphorylates receptor‐like cytoplasmic kinases PBL34/PBL35/PBL36 to activate immune responses.Bacterial pathogen P. syringae inhibits LORE via the secreted tyrosine phosphatase HopAO1. [ABSTRACT FROM AUTHOR]

Understanding the molecular drivers and feedback loops of osteoarthritis (OA) may provide future therapeutic strategies to modulate the disease progression. The current paradigm of OA is evolving from a purely mechanical disease caused by cartilage wear toward a complex biological response connecting biomechanics, inflammation, and the immune system. The view of OA as a chronic wound highlights the role inflammation plays and also the body's attempts to repair an ongoing injury. Inflammatory signals, including cytokines such as interleukin‐1 and tissue necrosis factor α, surface‐expressed pattern recognition receptors such as toll‐like receptors 2 and 4, complement factors such as C5, as well as pathogen‐associated molecular patterns and damage‐associated molecular patterns drive the enzymatic cascade that degrades cartilage matrix in OA. Considering the joint as an entire organ, interactions between the cells that reside in the synovium including macrophages and other immune cells, appear to drive enzymatic activity in cartilage, which, in turn, feeds signals back to the synovium that continues stimulating degradation in a feed‐forward loop. This review will explore the potential roles of immune cells such as macrophages and T cells in the synovium in both stimulating and modulating the inflammatory response in OA. © 2019 Orthopedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:253‐257, 2020 [ABSTRACT FROM AUTHOR]

The mechanisms involved in the induction of allergic sensitization by pollen are not fully understood. Within the last few decades, findings from epidemiological and experimental studies support the notion that allergic sensitization is not only dependent on the genetics of the host and environmental factors, but also on intrinsic features of the allergenic source itself. In this review, we summarize the current concepts and newest advances in research focusing on the initial mechanisms inducing pollen sensitization. Pollen allergens are embedded in a complex and heterogeneous matrix composed of a myriad of bioactive molecules that are co‐delivered during the allergic sensitization. Surprisingly, several purified allergens were shown to lack inherent sensitizing potential. Thus, growing evidence supports an essential role of pollen‐derived components co‐delivered with the allergens in the initiation of allergic sensitization. The pollen matrix, which is composed by intrinsic molecules (e.g. proteins, metabolites, lipids, carbohydrates) and extrinsic compounds (e.g. viruses, particles from air pollutants, pollen‐linked microbiome), provide a specific context for the allergen and has been proposed as a determinant of Th2 polarization. In addition, the involvement of various pattern recognition receptors (PRRs), secreted alarmins, innate immune cells, and the dependency of DCs in driving pollen‐induced Th2 inflammatory processes suggest that allergic sensitization to pollen most likely results from particular combinations of pollen‐specific signals rather than from a common determinant of allergenicity. The exact identification and characterization of such pollen‐derived Th2‐polarizing molecules should provide mechanistic insights into Th2 polarization and pave the way for novel preventive and therapeutic strategies against pollen allergies. [ABSTRACT FROM AUTHOR]

Background: Germline‐encoded innate immune pattern recognition receptors (PRR) are expressed at epithelial surfaces and modulate epithelial defenses. Evidence suggests that stimulation of the Toll‐like receptor (TLR) family of PRR may regulate epithelial barrier integrity by upregulating tight junction (TJ) complex protein expression, but it is not known whether this mechanism is utilized in esophageal epithelial cells. TJ complex proteins maintain intact barrier function and are dysregulated in atopic disorders including eosinophilic esophagitis. Methods: Pattern recognition receptors expression was assessed in EoE and control primary esophageal epithelial cells, demonstrating robust expression of TLR2 and TLR3. The three‐dimensional air‐liquid interface culture (ALI) model was used to test whether TLR2 or TLR3 stimulation alters epithelial barrier function using an in vitro model of human epithelium. Transepithelial electrical resistance (TEER) and FITC‐Dextran permeability were evaluated to assess membrane permeability. ALI cultures were evaluated by histology, immunohistochemistry, Western blotting, and chromatin immunoprecipitation (ChIP). Results: TLR3 stimulation did not change TEER in the ALI model. TLR2 stimulation increased TEER (1.28‐ to 1.31‐fold) and decreased paracellular permeability to FITC‐Dextran, and this effect was abolished by treatment with anti‐TLR2 blocking antibody. TJ complex proteins claudin‐1 and zonula occludens‐1 were upregulated following TLR2 stimulation, and ChIP assay demonstrated altered histone 4 acetyl binding at the TJP1 enhancer and CLDN1 enhancer and promoter following zymosan treatment, implying the occurrence of durable chromatin changes. Conclusions: Our findings implicate the TLR2 pathway as a potential regulator of esophageal epithelial barrier function and suggest that downstream chromatin modifications are associated with this effect. [ABSTRACT FROM AUTHOR]

Virus invasion triggers host immune responses, in particular, innate immune responses. Pathogen-associated molecular patterns of viruses (such as ds RNA, ss RNA, or viral proteins) released during virus replication are detected by the corresponding pattern-recognition receptors of the host, and innate immune responses are induced. Through production of type-I and type- III interferons as well as various other cytokines, the host innate immune system forms the frontline to protect host cells and inhibit virus infection. Not surprisingly, viruses have evolved diverse strategies to counter this antiviral system. In this review, we discuss the multiple strategies used by proteases of positive-sense single-stranded RNA viruses of the families Picornaviridae, Coronaviridae, and Flaviviridae, when counteracting host innate immune responses. [ABSTRACT FROM AUTHOR]

Pathogen recognition, signaling transduction pathways, and effector mechanisms are necessary steps of innate immune responses that play key roles in the early phase of defense and in the stimulation of the later specific response of adaptive immunity. Here, we argue that in addition to the direct recognition of conserved common structural and functional molecular signatures of microorganisms using pattern recognition receptors, hosts can mount an immune response following the sensing of disruption in homeostasis as proximal reporters for infections. Surveillance of disruption of core cellular activities leading to defense responses is a flexible strategy that requires few additional components and that can effectively detect relevant threats. It is likely to be evolutionarily very conserved and ancient because it is operational in organisms that lack pattern recognition triggered immunity. A homeostasis disruption model of immune response initiation and modulation has broad implications for pathophysiology and treatment of disease and might constitute an often overlooked but central component of a comprehensive conceptual framework for innate immunity. [ABSTRACT FROM AUTHOR]

The mechanisms involved in the induction of allergic sensitization by pollen are not fully understood. Within the last few decades, findings from epidemiological and experimental studies support the notion that allergic sensitization is not only dependent on the genetics of the host and environmental factors, but also on intrinsic features of the allergenic source itself. In this review, we summarize the current concepts and newest advances in research focusing on the initial mechanisms inducing pollen sensitization. Pollen allergens are embedded in a complex and heterogeneous matrix composed of a myriad of bioactive molecules that are co-delivered during the allergic sensitization. Surprisingly, several purified allergens were shown to lack inherent sensitizing potential. Thus, growing evidence supports an essential role of pollen-derived components co-delivered with the allergens in the initiation of allergic sensitization. The pollen matrix, which is composed by intrinsic molecules (e.g. proteins, metabolites, lipids, carbohydrates) and extrinsic compounds (e.g. viruses, particles from air pollutants, pollen-linked microbiome), provide a specific context for the allergen and has been proposed as a determinant of Th2 polarization. In addition, the involvement of various pattern recognition receptors (PRRs), secreted alarmins, innate immune cells, and the dependency of DCs in driving pollen-induced Th2 inflammatory processes suggest that allergic sensitization to pollen most likely results from particular combinations of pollen-specific signals rather than from a common determinant of allergenicity. The exact identification and characterization of such pollen-derived Th2-polarizing molecules should provide mechanistic insights into Th2 polarization and pave the way for novel preventive and therapeutic strategies against pollen allergies. [ABSTRACT FROM AUTHOR]