Cutting edge: CATERPILLER: a large family of mammalian genes containing CARD, pyrin, nucleotide-binding, and leucine-rich repeat domains

NLRs in tumor chemotherapy resistance: A double-edged sword

Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are a numerous family of cytoplasmic proteins. Members of this family not only function as innate immune sensors, but also serve as transcriptional regulators of major histocompatibility complex class II (MHC II) and major histocompatibility complex class I (MHC I) genes to activate adaptive immunity. Furthermore, NLRs are involved in mediating various signaling pathways, including the inflammasome. To date, extensive research has been conducted on the contradictory roles and mechanisms of NLRs in the occurrence, development, invasion, and metastasis of tumors within the tumor microenvironment (TME). The double-edged sword effect (either positive or negative role) of NLRs in the treatment of malignant tumors has attracted increasing attention in recent years, making these a promising bidirectional therapeutic target for such tumors. Rational utilization of the double-edged sword nature of NLRs can provide a feasible solution for improving the efficacy of malignant tumor treatment and overcoming chemotherapy resistance. This article provides a systematic review of the influence of the NLR family on chemosensitivity in different malignant tumors and the regulatory mechanisms of their upstream and downstream signaling pathways. In doing do, we aim to elucidate the dual role of NLRs in promoting and combating tumor chemotherapy resistance, and elucidate their application value in tumor chemotherapy resistance.

The role of NLRP3 and NLRP12 inflammasomes in glioblastoma

Glioblastoma (GBM) is the deadliest malignant brain tumor, with a survival of less than 14 months after diagnosis. The highly invasive nature of GBM makes total surgical resection challenging, leading to tumor recurrence and declined survival. The heterocellular composition of the GBM reprograms its microenvironment, favoring tumor growth, proliferation, and migration. The innate immune cells in the GBM tumor microenvironment, including microglia, astrocytes, and macrophages, express pattern recognition receptors such as NLRs (Nucleotide-binding domain and leucine-rich repeat-containing) that sense pathogen- and damage-associated molecular patterns initiating inflammation. Upon activation, NLRP3 promotes inflammation by NLRP3 inflammasome formation. Auto-proteolytic cleavage and activation of Caspase-1 within the inflammasome leads to caspase-1-mediated cleavage, activation, and conversion of pro-IL-1ß and pro-IL-18 to IL-1ß and IL-18, leading to pyroptosis. In contrast, NLRP12 downregulates inflammatory responses in microglia and macrophages by regulating the NF-κB pathway. NLRP3 and NLRP12 have been implicated in the disease pathophysiology of several cancers with cell-context-dependent, pro- or anti-tumorigenic roles. In this review, we discuss the current literature on the mechanistic roles of NLRP3 and NLRP12 in GBM and the gaps in the scientific literature in the context of GBM pathophysiology with potential for targeted therapeutics.

Porcine NLRC3 specially binds short dsDNA to regulate cGAS activation

Host immune system has evolved multiple sensors to detect pathogenic and damaged DNA, where precise regulation is critical for distinguishing self from non-self. Our previous studies showed that NLRC3 is an inhibitory nucleic acid sensor that binds to viral DNA and thereby unleashing STING activation. In this study, we demonstrate that human NLRC3 favors long dsDNA, while porcine NLRC3 shows an affinity for shorter dsDNA. Mechanistically, a conserved arginine residue within the leucine-rich repeats of primates NLRC3 forms a structural bridge facilitating the binding of long dsDNA. Conversely, a glycine residue that replaces the arginine in non-primates disrupts this bridge. Furthermore, porcine NLRC3 negatively regulates type I interferon by interacting with cyclic GMP-AMP synthase (cGAS) to inhibit its DNA binding, thereby preventing cGAS activation. These results reveal an unrecognized mechanism by which a species-specific amino acid variation of NLRC3 influences nucleic acid recognition, providing insights into the evolution of innate immunity to pathogens.

Nod-like receptors: The relevant elements of glioblastoma`s prognostic puzzle

Despite considerable improvements in understanding the biology of glioblastoma (GB), it still remains the most lethal type of brain tumor in adults. The role of innate immune cells in the development of GB was recently described. In particular, the tumor-immune cell interactions are thought to be critical in enabling tumor tolerance and even protection against therapeutics. Interestingly, the GB cells express proteins belonging to the family of intracellular pattern-recognition receptors, namely the NOD-like receptors (NLRs). Their activation may trigger the formation of the inflammasome complex leading to the secretion of mature IL-1β and IL-18 and thus resulting in cell death. Intrudingly, the expression of most NLRs was found to be correlated with tumor progression and poor prognosis. We speculate that recognizing the role of NOD-like receptors in GB has the potential to improve the effectiveness of diagnostic tools and prognosis, while also encouraging the development of novel precision medicine-based therapies.

Cadmium activates the innate immune system through the AIM2 inflammasome

Cadmium (Cd) is a widely used heavy metal and has recently been recognized as a possible source of human toxicity due to its ability to accumulate in organs. Accumulation of heavy metals has several adverse effects, including inducing inflammation, in multiple organs, such as the testis. However, how Cd ions are sensed by host cells and how tissue inflammation eventually occurs remains unclear. Here, we show that Cd activates the AIM2 inflammasome by mediating genomic DNA release into the cytoplasm after DNA damage via oxidative stress, to trigger IL-1β secretion and pyroptosis. Specifically, the toxicity effects induced by Cd in cells were prevented by melatonin, which served as an antagonist of oxidative stress. Accordingly, in a mouse model, Cd-induced inflammation in the testis and consequential male reproductive dysfunction were effectively reversed by melatonin. Thus, our results suggest a function of AIM2 in Cd-mediated testis inflammation and identify AIM2 as a major pattern recognition receptor in response to heavy metal Cd ions.

NLRP3 inflammasome in atherosclerosis: Mechanisms and targeted therapies

Atherosclerosis (AS) is the primary pathology behind various cardiovascular diseases and the leading cause of death and disability globally. Recent evidence suggests that AS is a chronic vascular inflammatory disease caused by multiple factors. In this context, the NLRP3 inflammasome, acting as a signal transducer of the immune system, plays a critical role in the onset and progression of AS. The NLRP3 inflammasome is involved in endothelial injury, foam cell formation, and pyroptosis in AS. Therefore, targeting the NLRP3 inflammasome offers a new treatment strategy for AS. This review highlights the latest insights into AS pathogenesis and the pharmacological therapies targeting the NLRP3 inflammasome, focusing on optimal targets for small molecule inhibitors. These insights are valuable for rational drug design and the pharmacological assessment of new targeted NLRP3 inflammasome inhibitors in treating AS.

HLA-C expression in extravillous trophoblasts is determined by an ELF3-NLRP2/NLRP7 regulatory axis

The distinct human leukocyte antigen (HLA) class I expression pattern of human extravillous trophoblasts (EVT) endows them with unique tolerogenic properties that enable successful pregnancy. Nevertheless, how this process is elaborately regulated remains elusive. Previously, E74 like ETS transcription factor 3 (ELF3) was identified to govern high-level HLA-C expression in EVT. In the present study, ELF3 is found to bind to the enhancer region of two adjacent NOD-like receptor (NLR) genes, NLR family pyrin domain-containing 2 and 7 (NLRP2, NLRP7). Notably, our analysis of ELF3-deficient JEG-3 cells, a human choriocarcinoma cell line widely used to study EVT biology, suggests that ELF3 transactivates NLRP7 while suppressing the expression of NLRP2. Moreover, we find that NLRP2 and NLRP7 have opposing effects on HLA-C expression, thus implicating them in immune evasion at the maternal-fetal interface. We confirmed that NLRP2 suppresses HLA-C levels and described a unique role for NLRP7 in promoting HLA-C expression in JEG-3. These results suggest that these two NLR genes, which arose via gene duplication in primates, are fine-tuned by ELF3 yet have acquired divergent functions to enable proper expression levels of HLA-C in EVT, presumably through modulating the degradation kinetics of IkBα. Targeting the ELF3-NLRP2/NLRP7-HLA-C axis may hold therapeutic potential for managing pregnancy-related disorders, such as recurrent hydatidiform moles and fetal growth restriction, and thus improve placental development and pregnancy outcomes.

NLRC5 senses NAD+ depletion, forming a PANoptosome and driving PANoptosis and inflammation

NLRs constitute a large, highly conserved family of cytosolic pattern recognition receptors that are central to health and disease, making them key therapeutic targets. NLRC5 is an enigmatic NLR with mutations associated with inflammatory and infectious diseases, but little is known about its function as an innate immune sensor and cell death regulator. Therefore, we screened for NLRC5's role in response to infections, PAMPs, DAMPs, and cytokines. We identified that NLRC5 acts as an innate immune sensor to drive inflammatory cell death, PANoptosis, in response to specific ligands, including PAMP/heme and heme/cytokine combinations. NLRC5 interacted with NLRP12 and PANoptosome components to form a cell death complex, suggesting an NLR network forms similar to those in plants. Mechanistically, TLR signaling and NAD+ levels regulated NLRC5 expression and ROS production to control cell death. Furthermore, NLRC5-deficient mice were protected in hemolytic and inflammatory models, suggesting that NLRC5 could be a potential therapeutic target.

Host Innate Antiviral Response to Influenza A Virus Infection: From Viral Sensing to Antagonism and Escape

Influenza virus possesses an RNA genome of single-stranded, negative-sensed, and segmented configuration. Influenza virus causes an acute respiratory disease, commonly known as the "flu" in humans. In some individuals, flu can lead to pneumonia and acute respiratory distress syndrome. Influenza A virus (IAV) is the most significant because it causes recurring seasonal epidemics, occasional pandemics, and zoonotic outbreaks in human populations, globally. The host innate immune response to IAV infection plays a critical role in sensing, preventing, and clearing the infection as well as in flu disease pathology. Host cells sense IAV infection through multiple receptors and mechanisms, which culminate in the induction of a concerted innate antiviral response and the creation of an antiviral state, which inhibits and clears the infection from host cells. However, IAV antagonizes and escapes many steps of the innate antiviral response by different mechanisms. Herein, we review those host and viral mechanisms. This review covers most aspects of the host innate immune response, i.e., (1) the sensing of incoming virus particles, (2) the activation of downstream innate antiviral signaling pathways, (3) the expression of interferon-stimulated genes, (4) and viral antagonism and escape.

The NLR family of innate immune and cell death sensors

Nucleotide-binding oligomerization domain (NOD)-like receptors, also known as nucleotide-binding leucine-rich repeat receptors (NLRs), are a family of cytosolic pattern recognition receptors that detect a wide variety of pathogenic and sterile triggers. Activation of specific NLRs initiates pro- or anti-inflammatory signaling cascades and the formation of inflammasomes-multi-protein complexes that induce caspase-1 activation to drive inflammatory cytokine maturation and lytic cell death, pyroptosis. Certain NLRs and inflammasomes act as integral components of larger cell death complexes-PANoptosomes-driving another form of lytic cell death, PANoptosis. Here, we review the current understanding of the evolution, structure, and function of NLRs in health and disease. We discuss the concept of NLR networks and their roles in driving cell death and immunity. An improved mechanistic understanding of NLRs may provide therapeutic strategies applicable across infectious and inflammatory diseases and in cancer.

Regulation of NF-κB signaling by NLRC (NLRC3-like) gene in the common carp (Cyprinus carpio)

Among teleost NLRs, NLR-C subfamily is a large group of proteins that were teleost-specific and evolution analysis showed that NLR-Cs are most likely to evolve from NLRC3 gene (thus also called as NLRC3Ls). Presently, although there have been rich studies investigating teleost NLRC3 and NLRC3L, the data on the regulatory mechanism was limited. In this study, immune regulation of inflammatory signaling pathway mediated by common carp NLRC3L gene (CcNLRC) has been investigated. Confocal microscopy analysis showed that CcNLRC was located in cytoplasm, and in HEK293T cells, dual-luciferase reporter assay showed the regulation of NF-κB signaling by CcNLRC, in which CcNLRC could alter/decrease RIPK2-induced activation of NF-κB. These results indicated that CcNLRC may function as a negative NLR in the regulation of inflammatory response in common carp. Our data will allow to gain more insights into the molecular mechanism of teleost specific NLR (NLRC3L).

Evolution of the Major Components of Innate Immunity in Animals

Innate immunity is present in all animals. In this review, we explore the main conserved mechanisms of recognition and innate immune responses among animals. In this sense, we discuss the receptors, critical for binding to pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs); the downstream signaling proteins; and transcription factors that govern immune responses. We also highlight conserved inflammatory mediators that are induced after the recognition of DAMPs and PAMPs. At last, we discuss the mechanisms that are involved in the regulation and/or generation of reactive oxygen species (ROS), influencing immune responses, like heme-oxygenases (HOs).

Biomaterials Functionalized with Inflammasome Inhibitors-Premises and Perspectives

This review aimed at searching literature for data regarding the inflammasomes' involvement in the pathogenesis of oral diseases (mainly periodontitis) and general pathologies, including approaches to control inflammasome-related pathogenic mechanisms. The inflammasomes are part of the innate immune response that activates inflammatory caspases by canonical and noncanonical pathways, to control the activity of Gasdermin D. Once an inflammasome is activated, pro-inflammatory cytokines, such as interleukins, are released. Thus, inflammasomes are involved in inflammatory, autoimmune and autoinflammatory diseases. The review also investigated novel therapies based on the use of phytochemicals and pharmaceutical substances for inhibiting inflammasome activity. Pharmaceutical substances can control the inflammasomes by three mechanisms: inhibiting the intracellular signaling pathways (Allopurinol and SS-31), blocking inflammasome components (VX-765, Emricasan and VX-740), and inhibiting cytokines mediated by the inflammasomes (Canakinumab, Anakinra and Rilonacept). Moreover, phytochemicals inhibit the inflammasomes by neutralizing reactive oxygen species. Biomaterials functionalized by the adsorption of therapeutic agents onto different nanomaterials could represent future research directions to facilitate multimodal and sequential treatment in oral pathologies.

Nlrc3 signaling is indispensable for hematopoietic stem cell emergence via Notch signaling in vertebrates

Hematopoietic stem and progenitor cells generate all the lineages of blood cells throughout the lifespan of vertebrates. The emergence of hematopoietic stem and progenitor cells is finely tuned by a variety of signaling pathways. Previous studies have revealed the roles of pattern-recognition receptors such as Toll-like receptors and RIG-I-like receptors in hematopoiesis. In this study, we find that Nlrc3, a nucleotide-binding domain leucine-rich repeat containing family gene, is highly expressed in hematopoietic differentiation stages in vivo and vitro and is required in hematopoiesis in zebrafish. Mechanistically, nlrc3 activates the Notch pathway and the downstream gene of Notch hey1. Furthermore, NF-kB signaling acts upstream of nlrc3 to enhance its transcriptional activity. Finally, we find that Nlrc3 signaling is conserved in the regulation of murine embryonic hematopoiesis. Taken together, our findings uncover an indispensable role of Nlrc3 signaling in hematopoietic stem and progenitor cell emergence and provide insights into inflammation-related hematopoietic ontogeny and the in vitro expansion of hematopoietic stem and progenitor cells.

The CATERPILLERS

This Pillars of Immunology article is a commentary on “Cutting Edge: CATERPILLER: A large family of mammalian genes containing CARD, pyrin, nucleotide-binding, and leucine-rich repeat domains,” a pivotal article written by J. A. Harton, M. W. Linhoff, J. Zhang, and J. P.-Y. Ting,” and published in The Journal of Immunology, in 2002. https://doi.org/10.4049/jimmunol.169.8.4088.

Alternatives to β-Lactams as Agents for the Management of Dentoalveolar Abscess

Dentoalveolar abscess are localized infections within the tooth or the surrounding alveolar bone, often resulting from untreated dental caries or dental trauma causing alveolar bone resorption or even loss. Serious consequences arising from the spread of a dental abscess can often lead to significant morbidity and mortality. The acute dentoalveolar abscess is a polymicrobial infection comprising strict anaerobes, such as anaerobic cocci i.e., Prevotella fusobacterium species, and facultative anaerobes i.e., Streptococci viridians and Streptococcus anginosus. Moreover, inappropriately managed dental infections can progress to severe submandibular space infections with associated serious complications, such as sepsis and airway obstruction. An audit of the Hull Royal Infirmary between 1999 and 2004 showed an increase in the number of patients presenting to oral and maxillofacial surgery services with dental sepsis. Thus, the scientific community is forced to focus on treatment strategies for the management of dentoalveolar abscess (DAA) and other related dental problems. The current treatment includes antibiotic therapy, including β-lactams and non-β- lactams drugs, but it leads to the development of resistant microorganisms due to improper and wide usage. Furthermore, the currently used β-lactam therapeutics is non-specific and easily hydrolyzed by the β-lactamase enzymes. Thus, the research focused on the non-β-lactams that can be the potential pharmacophore and helpful in the management of DAA, as the appropriate use and choice of antibiotics in dentistry plays an important role in antibiotic stewardship. The newer target for the choice is NLRP inflammasome, which is the major chemical mediator involved in dental problems. This review focused on pathogenesis and current therapeutics for the treatment of dentoalveolar abscesses.

PANoptosis: Mechanisms, biology, and role in disease

Cell death can be executed through distinct subroutines. PANoptosis is a unique inflammatory cell death modality involving the interactions between pyroptosis, apoptosis, and necroptosis, which can be mediated by multifaceted PANoptosome complexes assembled via integrating components from other cell death modalities. There is growing interest in the process and function of PANoptosis. Accumulating evidence suggests that PANoptosis occurs under diverse stimuli, for example, viral or bacterial infection, cytokine storm, and cancer. Given the impact of PANoptosis across the disease spectrum, this review briefly describes the relationships between pyroptosis, apoptosis, and necroptosis, highlights the key molecules in PANoptosome formation and PANoptosis activation, and outlines the multifaceted roles of PANoptosis in diseases together with a potential for therapeutic targeting. We also discuss important concepts and pressing issues for future PANoptosis research. Improved understanding of PANoptosis and its mechanisms is crucial for identifying novel therapeutic targets and strategies.

Immunobiodiversity: Conserved and specific immunity across land plants and beyond

Angiosperms represent most plants that humans cultivate, grow, and eat. However, angiosperms are only one of five major land plant lineages. As a whole lineage, plants also include algal groups. All these clades represent a tremendous genetic diversity that can be investigated to reveal the evolutionary history of any given mechanism. In this review, we describe the current model of the plant immune system, discuss its evolution based on the recent literature, and propose future directions for the field. In angiosperms, plant-microbe interactions have been intensively studied, revealing essential cell surface and intracellular immune receptors, as well as metabolic and hormonal defense pathways. Exploring diversity at the genomic and functional levels demonstrates the conservation of these pathways across land plants, some of which are beyond plants. On basis of the conserved mechanisms, lineage-specific variations have occurred, leading to diversified reservoirs of immune mechanisms. In rare cases, this diversity has been harnessed and successfully transferred to other species by integration of wild immune receptors or engineering of novel forms of receptors for improved resistance to pathogens. We propose that exploring further the diversity of immune mechanisms in the whole plant lineage will reveal completely novel sources of resistance to be deployed in crops.

NLRP12-associated autoinflammatory disease in Chinese adult patients: a single-centre study

BACKGROUND

NLRP12-associated autoinflammatory disease (NLRP12-AID) is an autosomal dominant autoinflammatory disorder caused by variants of NLRP12 gene. We aimed to report a cohort of Chinese adult patients with NLRP12-AID and summarised phenotypes and genotypes.

METHODS

Twenty patients were diagnosed with NLRP12-AID after performing whole-exome sequencing and were included in our cohort. Demographic information, clinical data and treatment response were collected and evaluated. A literature review of NLRP12-AID was performed, and the clinical features and mutated sites were summarised and compared with our cohort.

RESULTS

Among the 20 NLRP12-AID patients, the main clinical features of NLRP12-AID included fever, cutaneous rash, arthralgia/arthritis, pharyngitis/tonsillitis, lymphadenopathy, myalgia and abdominal pain/diarrhoea. Thirteen NLRP12 variants were detected as F402L, G39V, R1030X, R7G, E24A, Q90X, A218V, A259V, W581X, G729R, R859W, c.-150T>C and c.*126G>C. Glucocorticoids were used in 14 patients, immunosuppressive agents in 13, and tocilizumab in 2. Seventeen patients had good responses to therapy. When compared with 50 NLRP12-AID patients from other countries, Chinese patients had fewer variants in exon 3, higher incidences of cutaneous rash, pharyngitis/tonsillitis and lymphadenopathy. Among all these 70 NLRP12-AID patients, patients carrying non-exon-3 variants had higher frequencies of ocular involvement, pharyngitis/tonsillitis, headache and lymphadenopathy than those with exon-3 variants.

CONCLUSION

This is the largest cohort of NLRP12-AID in the world and seven novel variants of NLRP12 were identified. Chinese adult patients of NLRP12-AID had more non-specific symptoms such as pharyngitis/tonsillitis and lymphadenopathy when compared with patients from other countries, for which the less occurrence of exon-3 variants might be one possible reason.

A review of studies on the implication of NLRP3 inflammasome for Parkinson's disease and related candidate treatment targets

Parkinson's disease (PD) is a neurodegenerative disease for which the prevalence is second only to Alzheimer's disease (AD). This disease primarily affects people of middle and old age, significantly impacting their health and quality of life. The main pathological features include the degenerative nigrostriatal dopaminergic (DA) neuron loss and Lewy body (LB) formation. Currently, available PD medications primarily aim to alleviate clinical symptoms, however, there is no universally recognized therapy worldwide that effectively prevents, clinically treats, stops, or reverses the disease. Consequently, the evaluation and exploration of potential therapeutic targets for PD are of utmost importance. Nevertheless, the pathophysiology of PD remains unknown, and neuroinflammation mediated by inflammatory cytokines that prompts neuron death is fundamental for the progression of PD. The nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key complex of proteins linking the neuroinflammatory cascade in PD. Moreover, mounting evidence suggests that traditional Chinese medicine (TCM) alleviates PD by suppressing the NLRP3 inflammasome. This article aims to comprehensively review the available studies on the composition and activating mechanism of the NLRP3 inflammasome, along with its significance in PD pathogenesis and potential treatment targets. We also review natural products or synthetic compounds which reduce neuroinflammation via modulating NLRP3 inflammasome activity, aiming to identify new targets for future PD diagnosis and treatment through the exploration of NLRP3 inhibitors. Additionally, this review offers valuable references for developing new PD treatment methods.

The NLR gene family: from discovery to present day

The mammalian NLR gene family was first reported over 20 years ago, although several genes that were later grouped into the family were already known at that time. Although it is widely known that NLRs include inflammasome receptors and/or sensors that promote the maturation of caspase 1, IL-1β, IL-18 and gasdermin D to drive inflammation and cell death, the other functions of NLR family members are less well appreciated by the scientific community. Examples include MHC class II transactivator (CIITA), a master transcriptional activator of MHC class II genes, which was the first mammalian NBD-LRR-containing protein to be identified, and NLRC5, which regulates the expression of MHC class I genes. Other NLRs govern key inflammatory signalling pathways or interferon responses, and several NLR family members serve as negative regulators of innate immune responses. Multiple NLRs regulate the balance of cell death, cell survival, autophagy, mitophagy and even cellular metabolism. Perhaps the least discussed group of NLRs are those with functions in the mammalian reproductive system. The focus of this Review is to provide a synopsis of the NLR family, including both the intensively studied and the underappreciated members. We focus on the function, structure and disease relevance of NLRs and highlight issues that have received less attention in the NLR field. We hope this may serve as an impetus for future research on the conventional and non-conventional roles of NLRs within and beyond the immune system.

NLRP12-PANoptosome activates PANoptosis and pathology in response to heme and PAMPs

Cytosolic innate immune sensors are critical for host defense and form complexes, such as inflammasomes and PANoptosomes, that induce inflammatory cell death. The sensor NLRP12 is associated with infectious and inflammatory diseases, but its activating triggers and roles in cell death and inflammation remain unclear. Here, we discovered that NLRP12 drives inflammasome and PANoptosome activation, cell death, and inflammation in response to heme plus PAMPs or TNF. TLR2/4-mediated signaling through IRF1 induced Nlrp12 expression, which led to inflammasome formation to induce maturation of IL-1β and IL-18. The inflammasome also served as an integral component of a larger NLRP12-PANoptosome that drove inflammatory cell death through caspase-8/RIPK3. Deletion of Nlrp12 protected mice from acute kidney injury and lethality in a hemolytic model. Overall, we identified NLRP12 as an essential cytosolic sensor for heme plus PAMPs-mediated PANoptosis, inflammation, and pathology, suggesting that NLRP12 and molecules in this pathway are potential drug targets for hemolytic and inflammatory diseases.

The role of NOD-like receptors in innate immunity

The innate immune system in vertebrates and invertebrates relies on conserved receptors and ligands, and pathways that can rapidly initiate the host response against microbial infection and other sources of stress and danger. Research into the family of NOD-like receptors (NLRs) has blossomed over the past two decades, with much being learned about the ligands and conditions that stimulate the NLRs and the outcomes of NLR activation in cells and animals. The NLRs play key roles in diverse functions, ranging from transcription of MHC molecules to initiation of inflammation. Some NLRs are activated directly by their ligands, while other ligands may have indirect effects on the NLRs. New findings in coming years will undoubtedly shed more light on molecular details involved in NLR activation, as well as the physiological and immunological outcomes of NLR ligation.

Mechanism of NAIP-NLRC4 inflammasome activation revealed by cryo-EM structure of unliganded NAIP5

The nucleotide-binding domain (NBD), leucine rich repeat (LRR) domain containing protein family (NLR family) apoptosis inhibitory proteins (NAIPs) are cytosolic receptors that play critical roles in the host defense against bacterial infection. NAIPs interact with conserved bacterial ligands and activate the NLR family caspase recruitment domain containing protein 4 (NLRC4) to initiate the NAIP-NLRC4 inflammasome pathway. Here we found the process of NAIP activation is completely different from NLRC4. Our cryo-EM structure of unliganded mouse NAIP5 adopts an unprecedented wide-open conformation, with the nucleating surface fully exposed and accessible to recruit inactive NLRC4. Upon ligand binding, the winged helix domain (WHD) of NAIP5 undergoes roughly 20° rotation to form a steric clash with the inactive NLRC4, which triggers the conformational change of NLRC4 from inactive to active state. We also show the rotation of WHD places the 17-18 loop at a position that directly bind the active NLRC4 and stabilize the NAIP5-NLRC4 complex. Overall, these data provide structural mechanisms of inactive NAIP5, the process of NAIP5 activation and NAIP-dependent NLRC4 activation.

Overview of the anti-inflammatory function of the innate immune sensor NLRC3

The innate immune system is the first line of defense for the host against any microbial attack. It can quickly identify microorganisms and produce an immune response, removing pathogenic microorganisms. However, a strong immune response might lead to excessive inflammation and even autoimmune diseases. NLRC3 is an important regulator of innate immune system homeostasis. It is a member of the anti-inflammatory NLR family and can inhibit excessive immune response in the body. In this review, we primarily focused on the current research progress on NLRC3 and its potential application. It can decrease the production of pro-inflammatory cytokines by inhibiting the NF-κB, MAK-ERK, PI3K-mTOR, IL-6/JAK2/STAT3, and cGAS-STING pathways. It also inhibits inflammatory responses by interfering with the assembly and activity of the NLRP3 inflammasome complexes. Additionally, NLRC3 can also reduce the functions of some antigen-presenting cells and their ability to activate and polarize CD4⁺ T cells into Th1 and Th17 subsets. NLRC3 is closely related to the development of tumors, infectious diseases, autoimmune diseases, and AD. These diseases might be treated effectively by regulating the expression of NLRC3.

Induction of pyroptotic cell death as a potential tool for cancer treatment

Cancer is a complex pathological disease and the existing strategies for introducing chemotherapeutic agents have restricted potential due to a lack of cancer cell targeting specificity, cytotoxicity, bioavailability, and induction of multi-drug resistance. As a prospective strategy in tackling cancer, regulating the inflammatory pyroptosis cell death pathway has been shown to successfully inhibit the proliferation and metastasis of various cancer cell types. Activation of inflammasomes such as the NLRP3 results in pyroptosis through cleavage of gasdermins, which forms pores in the cell membranes, inducing membrane breakage, cell rupture, and death. Furthermore, pyroptotic cells release pro-inflammatory cytokines such as IL-1β and IL-18 along with various DAMPs that prime an auxiliary anti-tumor immune response. Thus, regulation of pyroptosis in cancer cells is a way to enhance their immunogenicity. However, immune escape involving myeloid-derived suppressor cells has limited the efficacy of most pyroptosis-based immunotherapy strategies. In this review, we comprehensively summarize the cellular and molecular mechanisms involved in the inflammasome-mediated pyroptosis pathways in cancer cells, exploring how it could modulate the tumor microenvironment and be beneficial in anti-cancer treatments. We discuss various existing therapeutic strategies against cancer, including immunotherapy, oncolytic virus therapy, and nanoparticle-based therapies that could be guided to trigger and regulate pyroptosis cell death in cancer cells, and reduce tumor growth and spread. These pyroptosis-based cancer therapies may open up fresh avenues for targeted cancer therapy approaches in the future and their translation into the clinic.

NLRP3 inflammasome activation mechanism and its role in autoimmune liver disease

The NLRP3 inflammasome is a multiprotein binding compound comprising NLRP3, connector protein ASC, and effector protein pro-caspase-1. When the NLRP3 inflammasome senses a danger signal from the host or pathogen, activated caspase-1 cleaves the precursors of interleukin (IL)-1β and IL-18 into mature proinflammatory cytokines, simultaneously causing lysis via the pore-forming protein gasdermin D. This induction of cell inflammatory pyroptosis suggests that it is a key process in the innate immune response to pathogens or cellular stress. Recent studies have shown that NLRP3 inflammasome also plays an important role in regulating autoimmune liver diseases, including autoimmune hepatitis, primary biliary cholangitis, and primary sclerosclerotic cholangitis. In this review, we summarize the structure, activation and modulation of the NLRP3 inflammasome, highlight the progress in research on the role of NLRP3 inflammasome in the occurrence and development of autoimmune liver diseases, and discuss potential strategies for targeting the NLRP3 inflammasome in the treatment of autoimmune liver diseases.

Posttranslational Regulation of Inflammasomes, Its Potential as Biomarkers and in the Identification of Novel Drugs Targets

In this review, we have summarized classical post-translational modifications (PTMs) such as phosphorylation, ubiquitylation, and SUMOylation of the different components of one of the most studied NLRP3, and other emerging inflammasomes. We will highlight how the discovery of these modifications have provided mechanistic insight into the biology, function, and regulation of these multiprotein complexes not only in the context of the innate immune system but also in adaptive immunity, hematopoiesis, bone marrow transplantation, as well and their role in human diseases. We have also collected available information concerning less-studied modifications such as acetylation, ADP-ribosylation, nitrosylation, prenylation, citrullination, and emphasized their relevance in the regulation of inflammasome complex formation. We have described disease-associated mutations affecting PTMs of inflammasome components. Finally, we have discussed how a deeper understanding of different PTMs can help the development of biomarkers and identification of novel drug targets to treat diseases caused by the malfunctioning of inflammasomes.

The All-Encompassing Importance of Innate Immunity

In their AAI President’s Addresses reproduced in this issue, Jeremy M. Boss, Ph.D. (AAI ’94; AAI President 2019–2020) and Jenny P.-Y. Ting, Ph.D. (AAI ’97; AAI President 2020–2021) welcomed attendees to the AAI annual meeting, Virtual IMMUNOLOGY2021™. Due to the SARS-CoV-2 pandemic and the cancellation of IMMUNOLOGY2020™, Dr. Boss and Dr. Ting each presented their respective President’s Address to open the meeting.

Inflammasome Contribution to the Activation of Th1, Th2, and Th17 Immune Responses

Inflammasomes are cytosolic polyprotein complexes formed in response to various external and internal stimuli, including viral and bacterial antigens. The main product of the inflammasome is active caspase 1 which proteolytically cleaves, releasing functional interleukin-1 beta (IL-1β) and interleukin-18 (IL-18). These cytokines play a central role in shaping immune response to pathogens. In this review, we will focus on the mechanisms of inflammasome activation, as well as their role in development of Th1, Th2, and Th17 lymphocytes. The contribution of cytokines IL-1β, IL-18, and IL-33, products of activated inflammasomes, are summarized. Additionally, the role of cytokines released from tissue cells in promoting differentiation of lymphocyte populations is discussed.

Impact of intracellular innate immune receptors on immunometabolism

Immunometabolism, which is the metabolic reprogramming of anaerobic glycolysis, oxidative phosphorylation, and metabolite synthesis upon immune cell activation, has gained importance as a regulator of the homeostasis, activation, proliferation, and differentiation of innate and adaptive immune cell subsets that function as key factors in immunity. Metabolic changes in epithelial and other stromal cells in response to different stimulatory signals are also crucial in infection, inflammation, cancer, autoimmune diseases, and metabolic disorders. The crosstalk between the PI3K-AKT-mTOR and LKB1-AMPK signaling pathways is critical for modulating both immune and nonimmune cell metabolism. The bidirectional interaction between immune cells and metabolism is a topic of intense study. Toll-like receptors (TLRs), cytokine receptors, and T and B cell receptors have been shown to activate multiple downstream metabolic pathways. However, how intracellular innate immune sensors/receptors intersect with metabolic pathways is less well understood. The goal of this review is to examine the link between immunometabolism and the functions of several intracellular innate immune sensors or receptors, such as nucleotide-binding and leucine-rich repeat-containing receptors (NLRs, or NOD-like receptors), absent in melanoma 2 (AIM2)-like receptors (ALRs), and the cyclic dinucleotide receptor stimulator of interferon genes (STING). We will focus on recent advances and describe the impact of these intracellular innate immune receptors on multiple metabolic pathways. Whenever appropriate, this review will provide a brief contextual connection to pathogenic infections, autoimmune diseases, cancers, metabolic disorders, and/or inflammatory bowel diseases.

Structural aspects of the MHC expression control system

The major histocompatibility complex (MHC) spans innate and adaptive immunity by presenting antigenic peptides to CD4⁺ and CD8⁺ T cells. Multiple transcription factors form an enhanceosome complex on the MHC promoter and recruit transcriptional machinery to activate gene transcription. Immune signals such as interferon-γ (IFN-γ) control MHC level by up-regulating components of the enhanceosome complex. As MHC plays crucial roles in immune regulation, alterations in the MHC enhanceosome structure will alter the pace of rapid immune responses at the transcription level and lead to various diseases related to the immune system. In this review, we discuss the current understanding of the MHC enhanceosome, with a focus on the structures of MHC enhanceosome components and the molecular basis of MHC enhanceosome assembly.

Nlrp3 Increases the Host's Susceptibility to Tularemia

Francisella tularensis (F. tularensis) is a Gram-negative, intracellular bacterium and the causative agent of a fatal human disease known as tularemia. The CDC has classified F. tularensis as a Tier 1 Category A select agent based on its ease of aerosolization, low infectious dose, past use as a bioweapon, and the potential to be used as a bioterror agent. Francisella has a unique replication cycle. Upon its uptake, Francisella remains in the phagosomes for a short period and then escapes into the cytosol, where the replication occurs. Francisella is recognized by cytosolic pattern recognition receptors, Absent In Melanoma 2 (Aim2) and Nacht LRR and PYD domains containing Protein 3 (Nlrp3). The recognition of Francisella ligands by Aim2 and Nlrp3 triggers the assembly and activation of the inflammasome. The mechanism of activation of Aim2 is well established; however, how Nlrp3 inflammasome is activated in response to F. tularensis infection is not known. Unlike Aim2, the protective role of Nlrp3 against Francisella infection is not fully established. This study investigated the role of Nlrp3 and the potential mechanisms through which Nlrp3 exerts its detrimental effects on the host in response to F. tularensis infection. The results from in vitro studies demonstrate that Nlrp3 dampens NF-κB and MAPK signaling, and pro-inflammatory cytokine production, which allows replication of F. tularensis in infected macrophages. In vivo, Nlrp3 deficiency results in differential expression of several genes required to induce a protective immune response against respiratory tularemia. Nlrp3-deficient mice mount a stronger innate immune response, clear bacteria efficiently with minimal organ damage, and are more resistant to Francisella infection than their wild-type counterparts. Together, these results demonstrate that Nlrp3 enhances the host's susceptibility to F. tularensis by modulating the protective innate immune responses. Collectively, this study advances our understanding of the detrimental role of Nlrp3 in tularemia pathogenesis.

Uptake, recognition and responses to peptidoglycan in the mammalian host

Microbiota, and the plethora of signalling molecules that they generate, are a major driving force that underlies a striking range of inter-individual physioanatomic and behavioural consequences for the host organism. Among the bacterial effectors, one finds peptidoglycan, the major constituent of the bacterial cell surface. In the steady-state, fragments of peptidoglycan are constitutively liberated from bacterial members of the gut microbiota, cross the gut epithelial barrier and enter the host system. The fate of these peptidoglycan fragments, and the outcome for the host, depends on the molecular nature of the peptidoglycan, as well the cellular profile of the recipient tissue, mechanism of cell entry, the expression of specific processing and recognition mechanisms by the cell, and the local immune context. At the target level, physiological processes modulated by peptidoglycan are extremely diverse, ranging from immune activation to small molecule metabolism, autophagy and apoptosis. In this review, we bring together a fragmented body of literature on the kinetics and dynamics of peptidoglycan interactions with the mammalian host, explaining how peptidoglycan functions as a signalling molecule in the host under physiological conditions, how it disseminates within the host, and the cellular responses to peptidoglycan.

A Comparative Overview of the Intracellular Guardians of Plants and Animals: NLRs in Innate Immunity and Beyond

Nucleotide-binding domain leucine-rich repeat receptors (NLRs) play important roles in the innate immune systems of both plants and animals. Recent breakthroughs in NLR biochemistry and biophysics have revolutionized our understanding of how NLR proteins function in plant immunity. In this review, we summarize the latest findings in plant NLR biology and draw direct comparisons to NLRs of animals. We discuss different mechanisms by which NLRs recognize their ligands in plants and animals. The discovery of plant NLR resistosomes that assemble in a comparable way to animal inflammasomes reinforces the striking similarities between the formation of plant and animal NLR complexes. Furthermore, we discuss the mechanisms by which plant NLRs mediate immune responses and draw comparisons to similar mechanisms identified in animals. Finally, we summarize the current knowledge of the complex genetic architecture formed by NLRs in plants and animals and the roles of NLRs beyond pathogen detection.

The rice LRR-like1 protein YELLOW AND PREMATURE DWARF 1 is involved in leaf senescence induced by high light

Senescence in plants is induced by endogenous physiological changes and exogenous stresses. In this study, we isolated two alleles of a novel rice (Oryza sativa) mutant, yellow and premature dwarf 1 (ypd1). The ypd1 mutants exhibited a yellow and dwarf phenotype from germination, and premature senescence starting at tillering. Moreover, the ypd1 mutants were sensitive to high light, which accelerated cell death and senescence. Consistent with their yellow phenotype, the ypd1 mutants had abnormal chloroplasts and lower levels of photosynthetic pigments. TUNEL assays together with histochemical staining demonstrated that ypd1 mutants showed cell death and that they accumulated reactive oxygen species. The ypd1 mutants also showed increased expression of genes associated with senescence. Map-based cloning revealed a G→A substitution in exon 6 (ypd1-1) and exon 13 (ypd1-2) of LOC_Os06g13050 that affected splicing and caused premature termination of the encoded protein. YPD1 was found to be preferentially expressed in the leaf and it encodes a LRR-like1 protein. Complementation, overexpression, and targeted deletion confirmed that the mutations in YPD1 caused the ypd1 phenotype. YPD1 was localized on the chloroplast membrane. Our results thus demonstrate that the novel rice LRR-like1 protein YPD1 affects chloroplast development and leaf senescence.

Biological Functions of Gasdermins in Cancer: From Molecular Mechanisms to Therapeutic Potential

Pyroptosis is a type of lytic programmed cell death triggered by various inflammasomes that sense danger signals. Pyroptosis has recently attracted great attention owing to its contributory role in cancer. Pyroptosis plays an important role in cancer progression by inducing cancer cell death or eliciting anticancer immunity. The participation of gasdermins (GSDMs) in pyroptosis is a noteworthy recent discovery. GSDMs have emerged as a group of pore-forming proteins that serve important roles in innate immunity and are composed of GSDMA-E and Pejvakin (PJVK) in human. The N-terminal domains of GSDMs, expect PJVK, can form pores on the cell membrane and function as effector proteins of pyroptosis. Remarkably, it has been found that GSDMs are abnormally expressed in several forms of cancers. Moreover, GSDMs are involved in cancer cell growth, invasion, metastasis and chemoresistance. Additionally, increasing evidence has indicated an association between GSDMs and clinicopathological features in cancer patients. These findings suggest the feasibility of using GSDMs as prospective biomarkers for cancer diagnosis, therapeutic intervention and prognosis. Here, we review the progress in unveiling the characteristics and biological functions of GSDMs. We also focus on the implication and molecular mechanisms of GSDMs in cancer pathogenesis. Investigating the relationship between GSDMs and cancer biology could assist us to explore new therapeutic avenues for cancer prevention and treatment.

microRNA in inflammatory bowel disease at a glance

Inflammatory bowel disease (IBD) as a chronic inflammation in colon and small intestine has two subtypes: ulcerative colitis (UC) and Crohn's disease (CD). Genome studies have shown that UC and CD are related to microRNAs (miRNAs) expression in addition to environmental factors. This article reviews important researches that have recently been done on miRNAs roles in CD and UC disease. First, miRNA is introduced and its biogenesis and function are discussed. Afterward, roles of miRNAs in inflammatory processes involved in IBD are showed. Finally, this review proposes some circulating and tissue-specific miRNAs, which are useful for CD and UC fast diagnosis and grade prediction. As a conclusion, miRNAs are efficient diagnostic molecules especially in IBD subtypes discrimination and can be used by microarray and real time PCR methods for disease detection and classification.

Structure, Activation and Regulation of NLRP3 and AIM2 Inflammasomes

The inflammasome is a three-component (sensor, adaptor, and effector) filamentous signaling platform that shields from multiple pathogenic infections by stimulating the proteolytical maturation of proinflammatory cytokines and pyroptotic cell death. The signaling process initiates with the detection of endogenous and/or external danger signals by specific sensors, followed by the nucleation and polymerization from sensor to downstream adaptor and then to the effector, caspase-1. Aberrant activation of inflammasomes promotes autoinflammatory diseases, cancer, neurodegeneration, and cardiometabolic disorders. Therefore, an equitable level of regulation is required to maintain the equilibrium between inflammasome activation and inhibition. Recent advancement in the structural and mechanistic understanding of inflammasome assembly potentiates the emergence of novel therapeutics against inflammasome-regulated diseases. In this review, we have comprehensively discussed the recent and updated insights into the structure of inflammasome components, their activation, interaction, mechanism of regulation, and finally, the formation of densely packed filamentous inflammasome complex that exists as micron-sized punctum in the cells and mediates the immune responses.

NLRC3 Delays the Progression of AD in APP/PS1 Mice via Inhibiting PI3K Activation

NLRC3 inhibits inflammatory responses. Neuroinflammation induces and accelerates the onset of Alzheimer's disease (AD). This study is aimed at investigating whether NLRC3 plays a role in neuroinflammation, Aβ accumulation, and neuroprotection in AD mice. 12-month-old APP/PS1 transgenic and C57 mice were used for studies in vivo. In vitro, organotypic hippocampal slices were cultured. We found that the expression of NLRC3 was downregulated in the brain tissues of APP/PS1 mice. Mice in the APP/PS1 group had a significant attenuation of learning and memory ability compared to the control group, and the ability was improved in APP/PS1 + LV-NLRC3 mice. The expressions of 6E10, GFAP, Iba1, and PI3K in the hippocampus and brains of APP/PS1 mice were significantly higher than those of the control group, while the expressions of NeuN were lower than that of the control group. With the overexpression of NLRC3 in the APP/PS1 + LV-NLRC3 group, the expressions of 6e10, GFAP, Iba1, and PI3K were significantly lower, while the expression of NeuN was significantly higher compared to the APP/PS1 group. NLRC3 colocalized with NeuN. PI3K activation with 740YP increased the expression of GFAP and Iba-1 in the hippocampus with the exogenous NLRC3 protein. We conclude that NLRC3 may play an important role in the development and progression of AD. Downregulation of NLRC3 can lead to the activation of PI3K, resulting in abnormal plaque deposition, glial cell activation, and neuron loss during AD. NLRC3 delays the progression of AD in APP/PS1 mice via inhibiting PI3K activation.

MHC class II transactivator CIITA induces cell resistance to Ebola virus and SARS-like coronaviruses

Recent outbreaks of Ebola virus (EBOV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have exposed our limited therapeutic options for such diseases and our poor understanding of the cellular mechanisms that block viral infections. Using a transposon-mediated gene-activation screen in human cells, we identify that the major histocompatibility complex (MHC) class II transactivator (CIITA) has antiviral activity against EBOV. CIITA induces resistance by activating expression of the p41 isoform of invariant chain CD74, which inhibits viral entry by blocking cathepsin-mediated processing of the Ebola glycoprotein. We further show that CD74 p41 can block the endosomal entry pathway of coronaviruses, including SARS-CoV-2. These data therefore implicate CIITA and CD74 in host defense against a range of viruses, and they identify an additional function of these proteins beyond their canonical roles in antigen presentation.

NLRP3 Sensing of Diverse Inflammatory Stimuli Requires Distinct Structural Features

The NLRP3 inflammasome is central to host defense and implicated in various inflammatory diseases and conditions. While the favored paradigm of NLRP3 inflammasome activation stipulates a unifying signal intermediate that de-represses NLRP3, this view has not been tested. Further, structures within NLRP3 required for inflammasome activation are poorly defined. Here we demonstrate that while the NLRP3 LRRs are not auto-repressive and are not required for inflammasome activation by all agonists, distinct sequences within the NLRP3 LRRs positively and negatively modulate inflammasome activation by specific ligands. In addition, elements within the HD1/HD2 “hinge” of NLRP3 and the nucleotide-binding domain have contrasting functions depending upon the specific agonists. Further, while NLRP3 1–432 is minimally sufficient for inflammasome activation by all agonists tested, the pyrin, and linker domains (1–134) function cooperatively and are sufficient for inflammasome activation by certain agonists. Conserved cysteines 8 and 108 appear important for inflammasome activation by sterile, but not infectious insults. Our results define common and agonist-specific regions of NLRP3 that likely mediate ligand-specific responses, discount the hypothesis that NLRP3 inflammasome activation has a unified mechanism, and implicate NLRP3 as an integrator of agonist-specific, inflammasome activating signals.

NLRP12 in innate immunity and inflammation

Nucleotide-binding leucine-rich repeat-containing proteins, or NOD-like receptors (NLRs), are intracellular innate immune sensors that can regulate several signaling pathways, including MyD88- and TRIF-dependent pathways. In addition to these regulatory roles, some NLRs can assemble into multimeric protein complexes known as inflammasomes. NLRP12 is a member of the NLR family that contains an N-terminal pyrin domain, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat. It has been shown to play a role in forming an inflammasome in response to specific infections, and it can also function as a regulator of inflammatory signaling. During Yersinia pestis or Plasmodium chabaudi infection, NLRP12 induces the release of the inflammasome-dependent cytokines IL-1β and IL-18. These NLRP12-dependent cytokines confer protection against severe infections caused by these pathogens. Conversely, during infection with Salmonella enterica serovar Typhimurium, vesicular stomatitis virus, Klebsiella pneumoniae, or Mycobacterium tuberculosis, and in colonic tumorigenesis, NLRP12 acts as a negative regulator of the NFκB and MAPK signaling pathways. NLRP12 also negatively regulates canonical and non-canonical signaling in T cells and causes exacerbated autoimmune diseases. Furthermore, NLRP12 acts as a central component in maintaining intestinal inflammation and gut homeostasis. Therefore, the ability of NLRP12 to function as an inflammasome or as a negative regulator is context-dependent. In this review, we provide an overview of the NLR family members and summarize recent insights into the roles of NLRP12 as an inflammasome and as a negative regulator.

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics

Inflammasomes are a group of multimolecular intracellular complexes assembled around several innate immune proteins. Recognition of a diverse range of microbial, stress and damage signals by inflammasomes results in direct activation of caspase‐1, which subsequently induces the only known form of secretion of active interleukin‐1β and interleukin‐18. Although the importance of interleukin‐1β in the periodontium is not questioned, the impact of inflammasomes in periodontal disease and its potential for therapeutics in periodontology is still in its very early stages. Increasing evidence in preclinical models and human data strongly implicate the involvement of inflammasomes in a number of inflammatory, autoinflammatory and autoimmune disorders. Here we review: (a) the currently known inflammasome functions, (b) clinical/preclinical data supporting inflammasome involvement in the context of periodontal and comorbid diseases and (c) potential therapies targeting inflammasomes. To clarify further the inflammasome involvement in periodontitis, we present analyses of data from a large clinical study (n = 5809) that measured the gingival crevicular fluid‐interleukin‐1β and grouped the participants based on current periodontal disease classifications. We review data on 4910 European‐Americans that correlate 16 polymorphisms in the interleukin‐1B region with high gingival crevicular fluid‐interleukin‐1β levels. We show that inflammasome components are increased in diseased periodontal tissues and that the caspase‐1 inhibitor, VX‐765, inhibits ~50% of alveolar bone loss in experimental periodontitis. The literature review further supports that although patients clinically present with the same phenotype, the disease that develops probably has different underlying biological pathways. The current data indicate that inflammasomes have a role in periodontal disease pathogenesis. Understanding the contribution of different inflammasomes to disease development and distinct patient susceptibility will probably translate into improved, personalized therapies.

Link between CIITA rs3087456 polymorphism and the risk of laryngeal squamous cell carcinoma in a Chinese population

The class II trans-activator (CIITA) is the master regulator of the major histocompatibility complex (MHC) gene expression. CIITA mutations have been previously associated with several kinds of tumors, while the role of CIITA polymorphisms (rs3087456) in laryngeal squamous cell carcinoma (LSCC) is little known. We evaluate the link between CIITA polymorphisms and the existence of LSCC in patients. This study was conducted with 200 Chinese Han patients (LSCC) and 200 healthy control subjects. The association of CIITA genetic polymorphism rs3087456 with the risk of LSCC was assessed through pyrosequencing. The CIITA expression in LSCC tumor tissue and adjacent normal tissue was detected by immunohistochemistry (IHC) staining. The relationship between the genotype of rs3087456 in controls and in clinical pathology features in LSCC were analyzed, and in-silico analysis was also used for the CIITA gene. The in-silico analysis results showed that the CIITA gene is closely related to genes such as RFX5 and RFXAP. The IHC results showed that CIITA was highly expressed in LSCC tumor tissues, compared with the corresponding adjacent normal tissues. The AG, AG + AA, and A genotypes of rs3087456 of CIITA gene notably increased the risk of LSCC compared to the controls. Our study suggests that CIITA polymorphism (rs3087456) is associated with a higher risk of developing LSCC in a Chinese cohort.

The strategies of targeting the NLRP3 inflammasome to treat inflammatory diseases

The NLRP3 inflammasome is a cytoplasmic multiprotein complex, the assembly of which can be initiated in response to various exogenous or endogenous danger signals. Excessive activation of the NLRP3 inflammasome has been implicated in the pathogenesis of a wide variety of human inflammatory diseases, suggesting that the NLRP3 inflammasome is a potential target for the treatment of these diseases. However, clinical drugs targeting the NLRP3 inflammasome are still not available. Recent data have elucidated the different signaling pathways or events that can control NLRP3 inflammasome activation and have provided some potential compounds with anti-NLRP3 inflammasome activity. Here, we summarize the molecular mechanisms and diseases involved in NLRP3 inflammasome activation and discuss the potential strategies targeting different aspects of the NLRP3 inflammasome and its implications for the treatment of inflammatory diseases.

Emerging Roles for NLRC5 in Immune Diseases

Innate immunity activates the corresponding immune response relying on multiple pattern recognition receptors (PRRs) that includes pattern recognition receptors (PRRs), like NOD-like receptors (NLRs), RIG-I-like receptors (RLRs), and C-type lectin receptors (CLRs), which could accurately recognize invasive pathogens. In particular, NLRs belong to a large protein family of pattern recognition receptors in the cytoplasm, where they are highly correlated with activation of inflammatory response system followed by rapid clearance of invasive pathogens. Among the NLRs family, NLRC5, also known as NOD4 or NOD27, accounts for a large proportion and involves in immune responses far and wide. Notably, in the above response case of inflammation, the expression of NLRC5 remarkably increased in immune cells and immune-related tissues. However, the evidence for higher expression of NLRC5 in immune disease still remains controversial. It is noted that the growing evidence further accounts for the participation of NLRC5 in the innate immune response and inflammatory diseases. Moreover, NLRC5 has also been confirmed to exert a critical role in the control of regulatory diverse signaling pathways. Together with its broad participation in the occurrence and development of immune diseases, NLRC5 can be consequently treated as a potential therapeutic target. Nevertheless, the paucity of absolute understanding of intrinsic characteristics and underlying mechanisms of NLRC5 still make it hard to develop targeting drugs. Therefore, current summary about NLRC5 information is indispensable. Herein, current knowledge of NLRC5 is summarized, and research advances in terms of NLRC5 in characteristics, biological function, and regulatory mechanisms are reviewed.

Activation of NLRX1 by NX-13 Alleviates Inflammatory Bowel Disease through Immunometabolic Mechanisms in CD4+ T Cells

Inflammatory bowel disease (IBD) is a complex autoimmune disease with dysfunction in pattern-recognition responses, including within the NLR family. Nucleotide-binding oligomerization domain, leucine rich repeat containing X1 (NLRX1) is a unique NLR with regulatory and anti-inflammatory functions resulting in protection from IBD in mouse models. NX-13 is an orally active, gut-restricted novel drug candidate that selectively targets and activates the NLRX1 pathway locally in the gut. In vitro and in vivo efficacy of NLRX1 activation by NX-13 was examined. Oral treatment with NX-13 alleviates disease severity, colonic leukocytic infiltration, and cytokine markers of inflammation in three mouse models of IBD (dextran sulfate sodium, Mdr1a^-/-, and CD45RB^hi adoptive transfer). Treatment of naive CD4⁺ T cells with NX-13 in vitro decreases differentiation into Th1 and Th17 subsets with increased oxidative phosphorylation and decreased NF-κB activation and reactive oxygen species. With stimulation by PMA/ionomycin, TNF-α, or H₂O₂, PBMCs from ulcerative colitis patients treated with NX-13 had decreased NF-κB activity, TNF-α⁺ and IFN-γ⁺ CD4⁺ T cells and overall production of IL-6, MCP1, and IL-8. NX-13 activates NLRX1 to mediate a resistance to both inflammatory signaling and oxidative stress in mouse models and human primary cells from ulcerative colitis patients with effects on NF-κB activity and oxidative phosphorylation. NX-13 is a promising oral, gut-restricted NLRX1 agonist for treating IBD.