An activating NLRC4 inflammasome mutation causes autoinflammation with recurrent macrophage activation syndrome

Macrophage Activation Syndrome: Not Just for Rheumatologists Anymore

SYNOPSIS

Macrophage activation syndrome (MAS) is a term that was originally used to describe a hyperinflammatory syndrome that developed in some patients with rheumatologic diseases. It is now clear that MAS and hemophagocytic lymphohistiocytosis (HLH) are defined by the same core pattern of clinical symptoms and share an underlying pathophysiology of impaired cytolytic activity and IFNγ-driven cytokine storm. Given that these disorders are highly related, lessons learned from the management of MAS can provide insights into effective approaches for HLH, particularly the strategy to employ anti-cytokine therapies early in the disease course.

Genetics of Familial Hemophagocytic Lymphohistiocytosis (HLH)

Familial hemophagocytic lymphohistiocytosis (fHLH) represents a group of rare, inherited immune system disorders characterized by uncontrolled inflammatory responses. fHLH results from genetic mutations that impair CD8 T cell and natural killer cell cytotoxicity. Without treatment, fHLH is commonly fatal, but early diagnosis and treatment, including immunosuppressive therapy, and in many cases, an allogeneic hematopoietic stem cell transplant (HSCT), can improve overall outcomes. Genetic testing is critical for confirming the diagnosis, identifying specific gene mutations, assessing family members for carrier status or disease risk, and informing donor selection for HSCT.

Inflammasomopathies: mechanisms and disease signatures

Inflammasomes form in response to infection, cellular stress, or damage. Gain-of-function (GOF) mutations in inflammasome receptors have been identified as the underlying cause of severe inflammatory diseases, termed 'inflammasomopathies'. Recently, molecular interrogation of these diseases revealed several distinctions at the level of the tissue affected, the inflammatory mediators that drive disease progression, and the contribution of programmed cell death. In this review we discuss key emerging differences across inflammasomopathies and the distinct inflammatory patterns seen in patients. We discuss how programmed cell death influences the progression of inflammasomopathies and the role of plasma membrane rupture. Understanding the molecular disease signatures across inflammasomopathies provides crucial insights into identifying and treating the underlying disease and opens new avenues for therapeutic interventions.

Pyroptosis of pulmonary fibroblasts and macrophages through NLRC4 inflammasome leads to acute respiratory failure

The NAIP/NLRC4 inflammasome plays a pivotal role in the defense against bacterial infections, with its in vivo physiological function primarily recognized as driving inflammation in immune cells. Acute lung injury (ALI) is a leading cause of mortality in sepsis. In this study, we identify that the NAIP/NLRC4 inflammasome is highly expressed in both macrophages and pulmonary fibroblasts and that pyroptosis of these cells plays a critical role in lung injury. Mice challenged with gram-negative bacteria or flagellin developed lethal lung injury, characterized by reduced blood oxygen saturation, disrupted lung barrier function, and escalated inflammation. Flagellin-induced lung injury was protected in caspase-1 or GSDMD-deficient mice. These findings enhance our understanding of the NAIP/NLRC4 inflammasome's (patho)physiological function and highlight the significant role of inflammasome activation and pyroptosis in ALI during sepsis.

Nlrc4 Inflammasome Expression After Acute Myocardial Infarction in Rats

Acute myocardial necrosis activates the immune response and inflammatory processes. Although the initial response is helpful in restoring tissue injury, dysregulated and exacerbated inflammation contributes to the progression of cardiac remodeling. Inflammasomes play important roles in post-infarction inflammation. NALP1/NLRP1, NLRP 3, and NLRC4 are the best-known inflammasomes. NLRP3, which has received the most study in cardiovascular disease, has been linked to increased IL-1β (IL1B) production and caspase-1 activity, as well as impaired cardiac function. The role of NLRP1 and NLRC4 inflammasomes after acute myocardial infarction (MI) is poorly understood. We evaluated the expression of myocardial inflammasomes and inflammatory markers 72 h after MI in rats. Male Wistar rats were divided into Sham (n = 15) and MI (n = 16) groups. MI was induced by ligating the left anterior descending coronary artery. Infarct size was assessed by histology. Myocardial protein and gene expression was analyzed by Western blot and RT-qPCR, respectively. IL-1β (Il1b) concentrations in serum and heart macerate supernatant were evaluated by ELISA. Statistical analysis was performed using Student's t test. Rats with an MI size less than 30% of the total left ventricle (LV) area were excluded; infarct size was 46 ± 11% of the total LV area in MI. The interstitial collagen fraction was higher in MI. Nlrc4, caspase-1 (Casp1), and IL-1β (Il1b) protein expressions were higher in MI. Nlrp3, Nlrp1, ASC (Pycard), pro-caspase-1, and pro-IL-1β (Il1b) expressions did not differ between groups. Expression of the Nlrp3 and ASC (Pycard) genes, as well as myocardial and serum IL-1β (Il1b) concentrations, was higher in MI. Acute post-myocardial infarction inflammation is characterized by increased protein expression of Nlrc4, caspase-1, and interleukin-1β; increased gene expression of Nlrp3 and ASC (Pycard); and elevated serum and myocardial concentrations of interleukin-1β in combination with an increased myocardial collagen interstitial fraction.

Supersulfides: A Promising Therapeutic Approach for Autoinflammatory Diseases

Supersulfides are molecular species characterized by catenated sulfur moieties, including low-molecular-weight and protein-bound supersulfides. Emerging evidence suggests that these molecules, abundantly present in diverse organisms, play essential roles far beyond their chemical properties, such as functions in energy metabolism, protein stabilization, and antiviral defense. Recent studies highlight their regulatory effects on pattern-recognition receptors (PRRs) and associated signaling pathways-such as nucleotide oligomerization domain-like receptor signaling, toll-like receptor signaling, and type I interferon receptor signaling-critical for innate immunity and inflammatory responses. Dysregulation of these pathways is implicated in a heterogeneous group of autoinflammatory diseases, including inflammasomopathies, relopathies, and type I interferonopathies, respectively. Notably, both endogenous and synthetic supersulfide donors have recently shown promising inhibitory effects on PRR signaling, offering their potential as targeted therapies for managing autoinflammatory conditions. This review summarizes the fundamental biology of supersulfides and typical autoinflammatory diseases, focusing on their roles in innate immune and inflammatory responses, while exploring their therapeutic potential in these diseases.

Updates in the Management of Hereditary Periodic Fever Syndromes in Children

Periodic fever syndrome is characterized by three or more febrile episodes in six months, each occurring at least seven days apart. Immune dysregulation in systemic autoinflammatory syndromes involves innate immunity (neutrophils, monocytes, and macrophages) and cytokines, mainly IL-1, with tumor necrosis factor (TNF), interferon alpha and beta, IL-2, IL-12, IL-18, and IL-23. Treatment includes colchicine, corticosteroids, immunosuppressants, and biologics. Prebiologic screening should be done to rule out tuberculosis, HIV, hepatitis B, and hepatitis C. Monitoring includes biomarkers of inflammation, disease activity score, looking for disease-specific organ involvement/complications, and treatment-related adverse drug reactions. There are research gaps in determining standardized treatment for the majority of autoinflammatory syndromes, duration of treatment, novel targets for treatment, and long-term prognosis.

Decoding Immunobiology Through Genetic Errors of Immunity

Throughout biology, the pursuit of genotype-phenotype relationships has provided foundational knowledge upon which new concepts and hypotheses are built. Genetic perturbation, whether occurring naturally or in experimental settings, is the mainstay of mechanistic dissection in biological systems. The unbiased discovery of causal genetic lesions via forward genetics in patients who have a rare disease elucidates a particularly impactful set of genotype-phenotype relationships. Here, we review the field of genetic errors of immunity, often termed inborn errors of immunity (IEIs), in a framework aimed at highlighting the powerful real-world immunology insights provided collectively and individually by these (approximately) 500 disorders. By conceptualizing essential immune functions in a model of the adaptive arsenal of rapid defenses, we organize IEIs based on immune circuits in which sensors, relays, and executioners cooperate to carry out pathogen clearance functions in an effective yet regulated manner. We review and discuss findings from IEIs that not only reinforce known immunology concepts but also offer surprising phenotypes, prompting an opportunity to refine our understanding of immune system function.

Macrophage Activation Syndrome

Macrophage activation syndrome (MAS) is a state of immune hyperactivation that can result in life-threatening multisystem end-organ dysfunction. Often termed a "cytokine storm," MAS occurs among the rheumatic diseases most typically in Still's disease but also in systemic lupus erythematosus and Kawasaki disease. MAS can also accompany infection, malignancy, and inborn errors of immunity. This review provides a practical, evidence-based guide to the understanding, recognition, and management of MAS in children and adults, with a primary focus on MAS complicating Still's disease.

Ubiquitination of gasdermin D N-terminal domain directs its membrane translocation and pore formation during pyroptosis

Gasdermin D (GSDMD) is a critical pyroptosis mediator, consisting of one N-terminal pore-forming domain and one C-terminal auto-inhibitory domain. The free N-terminal domain (GD-NT), which is released through caspase-1/11 cleavage, exhibits distinct features from the full-length GSDMD (GD-FL), including oligomerization, membrane translocation, and pore-formation. However, the underlying mechanisms are not well elucidated. Here, we found that GD-NT, but not GD-FL, was massively ubiquitinated in cells. The K63-linked polyubiquitination of GD-NT at Lys236/237 (human/mouse), catalyzed by TRAF1, directly prompted its membrane translocation and pore-formation during pyroptosis. Inhibition of GD-NT ubiquitination via site-directed mutations or the UBA1 inhibitor PYR-41 suppressed cell death in several pyroptosis cell models. Additionally, applying PYR-41 in septic mice efficiently suppressed the release of IL-18 and TNFα. Thus, GD-NT ubiquitination is a key regulatory mechanism controlling its membrane localization and activation, which may provide a novel target for modulating immune activity in pyroptosis-related diseases.

T-ing up the storm: pathogenic cycling lymphocytes in the biology of macrophage activation syndrome

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are potentially fatal cytokine storm syndromes with clinical features including fever, pancytopenia, hepatosplenomegaly, coagulopathy, and progressive multiorgan system dysfunction. Mechanistically, HLH / MAS are driven by persistent activation of lymphoid and myeloid cells, but our understanding of the pathogenic cell populations remains incomplete.

MAIN BODY

In this Perspectives article, we provide an overview of the biology of HLH / MAS and the critical role of interferon-g in disease pathogenesis. We discuss the recent discovery of cycling lymphocytes in HLH / MAS marked by expression of CD38 and HLA-DR, which are primary producers of IFN-γ. The expansion of cycling lymphocytes correlates with disease activity and helps to distinguish HLH / MAS from clinical mimics. We demonstrate an approach to quantify CD38+HLA-DR+ cycling lymphocytes and evaluate their utility as a diagnostic biomarker for HLH / MAS. Lastly, we discuss the treatment of MAS, including potential therapeutic options to target these pathogenic lymphocytes.

CONCLUSION

Understanding of biology of cycling lymphocytes in HLH / MAS will facilitate the development of novel therapeutic approaches to overcome these fatal hyperinflammatory disorders.

The Osgin Gene Family: Underexplored Yet Essential Mediators of Oxidative Stress

The Osgin gene family consists of two members, Osgin1 and Osgin2, involved in the cellular oxidative stress response. While many members of this essential cellular pathway have been extensively characterized, the Osgin gene family, despite its broad phylogenetic distribution, has received far less attention. Here, we review published articles and open-source databases to synthesize the current research on the evolutionary history, structure, biochemical and physiological functions, expression patterns, and role in disease of the Osgin gene family. Although Osgin displays broad spatiotemporal expression during development and adulthood, there is ambiguity regarding the cellular functions of the OSGIN proteins. A recent study identified OSGIN-1 as a flavin-dependent monooxygenase, but the biochemical role of OSGIN-2 has not yet been defined. Moreover, while the Osgin genes are implicated as mediators of cell proliferation, apoptosis, and autophagy, these functions have not been connected to the enzymatic classification of OSGIN. Misregulation of Osgin expression has long been associated with various disease states, yet recent analyses highlight the mechanistic role of OSGIN in pathogenesis and disease progression, underscoring the therapeutic potential of targeting OSGIN. In light of these findings, we suggest further avenues of research to advance our understanding of this essential, yet underexplored, gene family.

[Autoinflammatory diseases associated with IL-18]

Autoinflammatory diseases (AIDs) are conditions characterized by dysfunction of innate immunity, causing systemic inflammation and various clinical symptoms. The field of AIDs has expanded due to improved comprehension of pathophysiological mechanisms and advancements in genomics techniques. A new emerging category of AIDs is characterized by a significant increase in interleukin 18 (IL-18), a pro-inflammatory cytokine synthesized in macrophages and activated by caspase 1 via various inflammasomes. IL-18 plays a role in the regulation of innate and adaptive immunity. IL-18 is involved in various functions, such as the proliferation, survival, and differentiation of immune cells, tissue infiltration of immune cells, polarization of immune responses, and production of other pro-inflammatory cytokines. This review analyzes the literature on IL-18 regarding its functions and its implications in the diagnosis and treatment of AIDs. IL-18-associated AIDs comprise Still's disease and diseases associated with mutations in NLRC4, XIAP, CDC42, and PSTPIP1, as well as IL-18BP deficiencies. With the exception of PSTPIP1-associated diseases, these conditions all carry a risk of macrophagic activation syndrome. Measuring IL-18 levels in serum can aid in the diagnosis, prognosis, and monitoring of these diseases. Therapies targeting IL-18 and its signaling pathways are currently under investigation.

Leveraging diverse cell-death patterns in diagnosis of sepsis by integrating bioinformatics and machine learning

Background

Sepsis is a life-threatening disease causing millions of deaths every year. It has been reported that programmed cell death (PCD) plays a critical role in the development and progression of sepsis, which has the potential to be a diagnosis and prognosis indicator for patient with sepsis.

Methods

Fourteen PCD patterns were analyzed for model construction. Seven transcriptome datasets and a single cell sequencing dataset were collected from the Gene Expression Omnibus database.

Results

A total of 289 PCD-related differentially expressed genes were identified between sepsis patients and healthy individuals. The machine learning algorithm screened three PCD-related genes, NLRC4, TXN and S100A9, as potential biomarkers for sepsis. The area under curve of the diagnostic model reached 100.0% in the training set and 100.0%, 99.9%, 98.9%, 99.5% and 98.6% in five validation sets. Furthermore, we verified the diagnostic genes in sepsis patients from our center via qPCR experiment. Single cell sequencing analysis revealed that NLRC4, TXN and S100A9 were mainly expressed on myeloid/monocytes and dendritic cells. Immune infiltration analysis revealed that multiple immune cells involved in the development of sepsis. Correlation and gene set enrichment analysis (GSEA) analysis revealed that the three biomarkers were significantly associated with immune cells infiltration.

Conclusions

We developed and validated a diagnostic model for sepsis based on three PCD-related genes. Our study might provide potential peripheral blood diagnostic candidate biomarkers for patients with sepsis.

Shigella OspF blocks rapid p38-dependent priming of the NAIP-NLRC4 inflammasome

The NAIP-NLRC4 inflammasome senses pathogenic bacteria by recognizing the cytosolic presence of bacterial proteins such as flagellin and type III secretion system (T3SS) subunits. In mice, the NAIP-NLRC4 inflammasome provides robust protection against bacterial pathogens that infect intestinal epithelial cells, including the gastrointestinal pathogen Shigella flexneri. By contrast, humans are highly susceptible to Shigella, despite the ability of human NAIP-NLRC4 to robustly detect Shigella T3SS proteins. Why the NAIP-NLRC4 inflammasome protects mice but not humans against Shigella infection remains unclear. We previously found that human THP-1 cells infected with Shigella lose responsiveness to NAIP-NLRC4 stimuli, while retaining sensitivity to other inflammasome agonists. Using mT3Sf, a "minimal Shigella" system, to express individual secreted Shigella effector proteins, we found that the OspF effector specifically suppresses NAIP-NLRC4-dependent cell death during infection. OspF was previously characterized as a phosphothreonine lyase that inactivates p38 and ERK MAP kinases. We found that p38 was critical for rapid priming of NAIP-NLRC4 activity, particularly in cells with low NAIP-NLRC4 expression. Overall, our results provide a mechanism by which Shigella evades inflammasome activation in humans, and describe a new mechanism for rapid priming of the NAIP-NLRC4 inflammasome.

IL-18 and IL-18BP: A Unique Dyad in Health and Disease

Interleukin-18 (IL-18) serves a dual function in the immune system, acting as a "double-edged sword" cytokine. Depending on the microenvironment and timing, IL-18 can either drive harmful inflammation or restore immune homeostasis. Pathologies characterized by elevated IL-18, recently proposed to be termed IL-18opathies, highlight the therapeutic potential for IL-18 blockade. IL-18 Binding Protein (IL-18BP) is one of only four natural cytokine antagonists encoded by a separate gene, distinguishing it from canonical soluble receptors. IL-18BP's exceptionally high affinity and slow dissociation rate make it an effective regulator of IL-18, essential for maintaining immune balance and influencing disease outcomes, and positions IL-18BP as a promising alternative to more aggressive treatments that carry risks of severe infections and other complications. Tadekinig alfa, the drug form of IL-18BP, represents a targeted therapy that modulates the IL-18/IL-18BP axis, offering a safe adverse-effect-free option. With orphan drug designation, Phase III clinical trial completion, and seven years of compassionate use, Tadekinig alfa holds promise in treating autoimmune and inflammatory diseases, cancer, and genetically linked disorders. Levels of IL-18, free IL-18 and IL-18BP, may serve as biomarkers for disease severity and therapeutic response. Given its pivotal role in immune balance, the IL-18/IL-18BP dyad has attracted interest from over ten pharmaceutical companies and startups, which are currently developing innovative strategies to either inhibit or enhance IL-18 activity depending on the therapeutic need. The review focuses on the features of the dyad members and screens the therapeutic approaches.

TLR priming licenses NAIP inflammasome activation by immunoevasive ligands

NLR family, apoptosis inhibitory proteins (NAIPs) detect bacterial flagellin and structurally related components of bacterial type III secretion systems (T3SS), and recruit NLR family CARD domain containing protein 4 (NLRC4) and caspase-1 into an inflammasome complex that induces pyroptosis. NAIP/NLRC4 inflammasome assembly is initiated by the binding of a single NAIP to its cognate ligand, but a subset of bacterial flagellins or T3SS structural proteins are thought to evade NAIP/NLRC4 inflammasome sensing by not binding to their cognate NAIPs. Unlike other inflammasome components such as NLRP3, AIM2, or some NAIPs, NLRC4 is constitutively present in resting macrophages and not known to be induced by inflammatory signals. Here, we demonstrate that Toll-like receptor (TLR)-dependent p38 mitogen-activated protein kinase signaling up-regulates NLRC4 transcription and protein expression in murine macrophages, which licenses NAIP detection of evasive ligands. In contrast, TLR priming in human macrophages did not up-regulate NLRC4 expression, and human macrophages remained unable to detect NAIP-evasive ligands even following priming. Critically, ectopic expression of either murine or human NLRC4 was sufficient to induce pyroptosis in response to immunoevasive NAIP ligands, indicating that increased levels of NLRC4 enable the NAIP/NLRC4 inflammasome to detect these normally evasive ligands. Altogether, our data reveal that TLR priming tunes the threshold for the murine NAIP/NLRC4 inflammasome to enable inflammasome responses against immunoevasive or suboptimal NAIP ligands. These findings provide insight into species-specific TLR regulation of NAIP/NLRC4 inflammasome activation.

Hemophagocytic lymphohistiocytosis: current treatment advances, emerging targeted therapy and underlying mechanisms

Hemophagocytic lymphohistiocytosis (HLH) is a rapidly progressing, life-threatening syndrome characterized by excessive immune activation, often presenting as a complex cytokine storm. This hyperactive immune response can lead to multi-organ failure and systemic damage, resulting in an extremely short survival period if left untreated. Over the past decades, although HLH has garnered increasing attention from researchers, there have been few advancements in its treatment. The cytokine storm plays a crucial role in the treatment of HLH. Investigating the detailed mechanisms behind cytokine storms offers insights into targeted therapeutic approaches, potentially aiding in early intervention and improving the clinical outcome of HLH patients. To date, there is only one targeted therapy, emapalumab targeting interferon-γ, that has gained approval for primary HLH. This review aims to summarize the current treatment advances, emerging targeted therapeutics and underlying mechanisms of HLH, highlighting its newly discovered targets potentially involved in cytokine storms, which are expected to drive the development of novel treatments and offer fresh perspectives for future studies. Besides, multi-targeted combination therapy may be essential for disease control, but further trials are required to determine the optimal treatment mode for HLH.

Somatic mutations in autoinflammatory and autoimmune disease

Somatic mutations (also known as acquired mutations) are emerging as common, age-related processes that occur in all cells throughout the body. Somatic mutations are canonically linked to malignant processes but over the past decade have been increasingly causally connected to benign diseases including rheumatic conditions. Here we outline the contribution of somatic mutations to complex and monogenic immunological diseases with a detailed review of unique aspects associated with such causes. Somatic mutations can cause early- or late-onset rheumatic monogenic diseases but also contribute to the pathogenesis of complex inflammatory and immune-mediated diseases, affect disease progression and define new clinical subtypes. Although even variants with a low variant allele fraction can be pathogenic, clonal dynamics could lead to changes over time in the proportion of mutant cells, with possible phenotypic consequences for the individual. Thus, somatic mutagenesis and clonal expansion have relevant implications in genetic testing and counselling. On the basis of both increased recognition of somatic diseases in clinical practice and improved technical and bioinformatic processes, we hypothesize that there will be an ever-expanding list of somatic mutations in various genes leading to inflammatory conditions, particularly in late-onset disease.

Inflammasome protein scaffolds the DNA damage complex during tumor development

Inflammasome sensors activate cellular signaling machineries to drive inflammation and cell death processes. Inflammasomes also control the development of certain diseases independently of canonical functions. Here, we show that the inflammasome protein NLR family CARD domain-containing protein 4 (NLRC4) attenuated the development of tumors in the Apcmin/+ mouse model. This response was independent of inflammasome signaling by NLRP3, NLRP6, NLR family apoptosis inhibitory proteins, absent in melanoma 2, apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1 and caspase-11. NLRC4 interacted with the DNA-damage-sensing ataxia telangiectasia and Rad3-related (ATR)-ATR-interacting protein (ATRIP)-Ewing tumor-associated antigen 1 (ETAA1) complex to promote the recruitment of the checkpoint adapter protein claspin, licensing the activation of the kinase checkpoint kinase-1 (CHK1). Genotoxicity-induced activation of the NLRC4-ATR-ATRIP-ETAA1 complex drove the tumor-suppressing DNA damage response and CHK1 activation, and further attenuated the accumulation of DNA damage. These findings demonstrate a noninflammatory function of an inflammasome protein in promoting the DNA damage response and mediating protection against cancer.

An improved understanding of pediatric chronic nonbacterial osteomyelitis pathophysiology informs current and future treatment

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease that primarily affects children and young people. It can cause significant pain, reduced function, bone swelling, and even (vertebral body) fractures. Because of a limited understanding of its pathophysiology, the treatment of CNO remains empiric and is based on relatively small case series, expert opinion, and personal experience. Several studies have linked pathological NOD-kike receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome activation and the resulting imbalance between pro- and anti-inflammatory cytokine expression with CNO. This agrees with elevated pro-inflammatory (mostly) monocyte-derived protein signatures in the blood of CNO patients that may be used as future diagnostic and/or prognostic biomarkers. Recently, rare variants in the P2RX7 gene, encoding for an ATP-dependent transmembrane channel, were linked with increased NLRP3 inflammasome assembly and prolonged monocyte/macrophage survival in CNO. Although the exact molecular mechanisms remain unclear, this will inform future target-directed and individualized treatment. This manuscript reviews most recent developments and their impact on diagnostic and therapeutic strategies in CNO.

Three cases of autoinflammatory disease with novel NLRC4 mutations, and the first mutation reported in the CARD domain of NLRC4 associated with autoinflammatory infantile enterocolitis (AIFEC)

BACKGROUND

Gain of function (GOF) mutations in NOD-like receptor family CARD-containing 4 protein (NLRC4) gene induce a wide spectrum of autoinflammatory phenotypes. Currently, we categorize them into four groups: familial cold autoinflammatory syndrome (FCAS)4, autoinflammatory infantile enterocolitis (AIFEC), NLRC4-macrophage associated syndrome (MAS), and neonatal-onset multisystem inflammatory disease (NOMID). The rarity and complexity of the disease necessitate the description of new cases and a reexamination of our understanding of the condition.

CASE PRESENTATIONS

We present three patients with NLRC4-GOF mutations and AIFEC phenotypes. The first patient is an infant girl with periodic fever, seizure, high inflammatory markers, and an episode of macrophage associated syndrome (MAS). History of recurrent fever episodes since childhood was reported in mother and maternal grandmother. A heterozygous mutation was found in CARD domain of NLRC4: c.A91C: p.Asn31His. The second patient is an adolescent boy with periodic fever, diarrhea, aphthous stomatitis, seizure, and central nervous system (CNS) vasculitis. A heterozygous mutation was found in NLRC4 gene: c.1202T > C. p. Val401Ala. The third patient is a child with chronic diarrhea and elevated inflammatory markers. We found a heterozygous mutation in NLRC4 gene: c.390delG: p.S132Afs*21. All mutations have been reported for the first time as NLRC4 mutations associated with autoinflammation. We introduced novel mutations in the CARD domain and between CARD and NBD domain in the first and third cases, respectively. All three children are under remission following treatment.

CONCLUSIONS

NLRC4-GOF mutations can be associated with autoinflammation with diverse symptoms. Given the rarity of the disease and the possibility of new mutations being identified, the existence of a phenotype/genotype correlation has yet to be thoroughly investigated. The variety in manifestations and severity spectrum mandates a variety of treatments. Adalimumab has shown favorable outcomes in our AIFEC cases.

Genetic and epigenetic dysregulation of innate immune mechanisms in autoinflammatory diseases

Dysregulation and hyperactivation of innate immune responses can lead to the onset of systemic autoinflammatory diseases. Monogenic autoinflammatory diseases are caused by inborn genetic errors and based on molecular mechanisms at play, can be divided into inflammasomopathies, interferonopathies, relopathies, protein misfolding, and endogenous antagonist deficiencies. On the other hand, more common autoinflammatory diseases are multifactorial, with both genetic and non-genetic factors playing an important role. During the last decade, long-term memory characteristics of innate immune responses have been described (also called trained immunity) that in physiological conditions provide enhanced host protection from pathogenic re-infection. However, if dysregulated, induction of trained immunity can become maladaptive, perpetuating chronic inflammatory activation. Here, we describe the mechanisms of genetic and epigenetic dysregulation of the innate immune system and maladaptive trained immunity that leads to the onset and perpetuation of the most common and recently described systemic autoinflammatory diseases.

NLRC4, inflammation and colorectal cancer (Review)

Chronic inflammation is recognized as a major risk factor for cancer and is involved in every phase of the disease. Inflammasomes are central to the inflammatory response and play a crucial role in cancer development. The present review summarizes the role of Nod‑like receptor C4 (NLRC4) in inflammation and colorectal cancer (CRC). Reviews of the literature were conducted using Web of Science, PubMed and CNKI, with search terms including 'NLRC4', 'colorectal cancer', 'auto‑inflammatory diseases' and 'prognosis'. Variants of NLRC4 can cause recessive immune dysregulation and autoinflammation or lead to ulcerative colitis as a heterozygous risk factor. Additionally, genetic mutations in inflammasome components may increase susceptibility to cancer. NLRC4 is considered a tumor suppressor in CRC. The role of NLRC4 in CRC signaling pathways is currently understood to involve five key aspects (caspase 1, NLRP3/IL‑8, IL‑1β/IL‑1, NAIP and p53). The mechanisms by which NLRC4 is involved in CRC are considered to be threefold (through pyroptosis, apoptosis, necroptosis and PANoptosis; regulating the immune response; and protecting intestinal epithelial cells to prevent CRC). However, the impact of NLRC4 mutations on CRC remains unclear. In conclusion, NLRC4 is a significant inflammasome that protects against CRC through various signaling pathways and mechanisms. The association between NLRC4 mutations and CRC warrants further investigation.

Non-Skewed X-inactivation Results in NF-κB Essential Modulator (NEMO) Δ-exon 5-autoinflammatory Syndrome (NEMO-NDAS) in a Female with Incontinentia Pigmenti

PURPOSE

Genetic hypomorphic defects in X chromosomal IKBKG coding for the NF-κB essential modulator (NEMO) lead to ectodermal dysplasia and immunodeficiency in males and the skin disorder incontinentia pigmenti (IP) in females, respectively. NF-κB essential modulator (NEMO) Δ-exon 5-autoinflammatory syndrome (NEMO-NDAS) is a systemic autoinflammatory disease caused by alternative splicing and increased proportion of NEMO-Δex5. We investigated a female carrier presenting with IP and NEMO-NDAS due to non-skewed X-inactivation.

METHODS

IKBKG transcripts were quantified in peripheral blood mononuclear cells isolated from the patient, her mother, and healthy controls using RT-PCR and nanopore sequencing. Corresponding proteins were analyzed by western blotting and flow cytometry. Besides toll-like receptor (TLR) and tumor necrosis factor (TNF) signaling, the interferon signature, cytokine production and X-inactivation status were investigated.

RESULTS

IP and autoinflammation with recurrent fever, oral ulcers, hepatitis, and neutropenia, but no immunodeficiency was observed in a female patient. Besides moderately reduced NEMO signaling function, type I interferonopathy, and elevated IL-18 and CXCL10 were found. She and her mother both carried the heterozygous variant c.613 C > T p.(Gln205*) in exon 5 of IKBKG previously reported in NEMO-deficient patients. However, X-inactivation was skewed in the mother, but not in the patient. Alternative splicing led to increased ratios of NEMO-Dex5 over full-length protein in peripheral blood cell subsets causing autoinflammation. Clinical symptoms partially resolved under treatment with TNF inhibitors.

CONCLUSION

Non-skewed X-inactivation can lead to NEMO-NDAS in females with IP carrying hypomorphic IKBKG variants due to alternative splicing and increased proportions of NEMO-∆ex5.

Activation of the helper NRC4 immune receptor forms a hexameric resistosome

Innate immune responses to microbial pathogens are regulated by intracellular receptors known as nucleotide-binding leucine-rich repeat receptors (NLRs) in both the plant and animal kingdoms. Across plant innate immune systems, "helper" NLRs (hNLRs) work in coordination with "sensor" NLRs (sNLRs) to modulate disease resistance signaling pathways. Activation mechanisms of hNLRs based on structures are unknown. Our research reveals that the hNLR, known as NLR required for cell death 4 (NRC4), assembles into a hexameric resistosome upon activation by the sNLR Bs2 and the pathogenic effector AvrBs2. This conformational change triggers immune responses by facilitating the influx of calcium ions (Ca2+) into the cytosol. The activation mimic alleles of NRC2, NRC3, or NRC4 alone did not induce Ca2+ influx and cell death in animal cells, suggesting that unknown plant-specific factors regulate NRCs' activation in plants. These findings significantly advance our understanding of the regulatory mechanisms governing plant immune responses.

Inflammatory profile of lower risk myelodysplastic syndromes

The precise link between inflammation and pathogenesis of myelodysplastic syndrome (MDS) is yet to be fully established. We developed a novel method to measure ASC/NLRP3 protein specks which are specific for the NLRP3 inflammasome only. We combined this with cytokine profiling to characterise various inflammatory markers in a large cohort of patients with lower risk MDS in comparison to healthy controls and patients with defined autoinflammatory disorders (AIDs). The ASC/NLRP3 specks were significantly elevated in MDS patients compared to healthy controls (p < 0.001) and these levels were comparable to those found in patients with AIDs. The distribution of protein specks positive only for ASC was different to ASC/NLRP3 ones suggesting that other ASC-containing inflammasome complexes might be important in the pathogenesis of MDS. Patients with MDS-SLD had the lowest levels of interleukin (IL)-1β, tumour necrosis factor (TNF), IL-23, IL-33, interferon (IFN) γ and IFN-α2, compared to other diagnostic categories. We also found that inflammatory cytokine TNF was positively associated with MDS progression to a more aggressive form of disease and IL-6 and IL-1β with time to first red blood cell transfusion. Our study shows that there is value in analysing inflammatory biomarkers in MDS, but their diagnostic and prognostic utility is yet to be fully validated.

New discoveries in the genetics and genomics of systemic juvenile idiopathic arthritis

INTRODUCTION

Systemic juvenile idiopathic arthritis (sJIA) is a severe inflammatory condition with onset in childhood. It is sporadic, but elements of its stereotypical innate immune responses are likely genetically encoded by both common variants with small effect sizes and rare variants with larger effects.

AREAS COVERED

Genomic investigations have defined the unique genetic architecture of sJIA. Identification of the class II HLA locus as the strongest sJIA risk factor for the first time brought attention to T lymphocytes and adaptive immune mechanisms in sJIA. The importance of the human leukocyte antigen (HLA) locus was reinforced by recognition that HLA-DRB1*15 alleles are strongly associated with development of drug reactions and sJIA-associated lung disease (sJIA-LD). At the IL1RN locus, genetic variation relates to both risk of sJIA and may also predict non-response to anakinra. Finally, rare genetic variants may have critical roles in disease complications, such as homozygous LACC1 mutations in families with an sJIA-like illness, and hemophagocytic lymphohistiocytosis (HLH) gene variants in some children with macrophage activation syndrome (MAS).

EXPERT OPINION

Genetic and genomic analysis of sJIA holds great promise for both basic discovery of the course and complications of sJIA, and may help guide personalized medicine and therapeutic decision-making.

Identification of Pyroptosis-Related Molecular Subtypes and Diagnostic Model development in Major Depressive Disorder

Major depressive disorder (MDD) is a prevalent psychological disorder associated with inflammation, with complex pathological mechanisms. Pyroptosis has been suggested to contribute to inflammation in central nervous system diseases. Little research, however, has examined what role pyroptosis played in MDD. In the present study, the differential expression pyroptosis-related genes (DE-PRGs) in MDD were identified from the GEO database (GSE98793 and GSE19738). Then, consensus clustering analysis was used to evaluate differences in MDD molecular subtypes characteristics based on PRGs. The characteristic diagnostic biomarkers for MDD were identified by Weighted Correlation Network Analysis (WGCNA) and multiple machine learning algorithms. Three intersection genes (GZMA, AKR1C3, and CD52) were obtained, which are expected to become potential biomarkers for MDD with excellent reliability and accuracy. Subsequently, the immune infiltration characteristics result indicated that the development of MDD is mediated by immune-related function, where three DE-PRGs were strongly related to the immune infiltration landscape of MDD. The biological experiments in vitro further proved that three unique PRGs are emerging as important players in MDD diagnosis. Our research aimed to provide novel ideas and biomarkers targeting MDD.

Fever, convulsions, and rash: a case report of neonatal lupus erythematosus with macrophage activation syndrome

Neonatal lupus erythematosus (NLE) is a rare acquired autoimmune disease associated with the entry of maternal antibodies into the fetal circulation via the placenta during pregnancy. Macrophage activation syndrome (MAS) is a severe hyperinflammatory disease. Herein, we present a case of NLE with MAS accompanied by fever, convulsions, and rash. High-dose gamma globulin and non-shock doses of steroids can be used as a first-line treatment for NLE with MAS. Fever can be a clinical manifestation of NLE, especially cutaneous lupus. Rash recession could be used to judge whether the disease is effectively controlled by treatment.

Gasdermin-E-mediated pyroptosis drives immune checkpoint inhibitor-associated myocarditis via cGAS-STING activation

Immune checkpoint inhibitor (ICI)-induced myocarditis involves intensive immune/inflammation activation; however, its molecular basis is unclear. Here, we show that gasdermin-E (GSDME), a gasdermin family member, drives ICI-induced myocarditis. Pyroptosis mediated by GSDME, but not the canonical GSDMD, is activated in myocardial tissue of mice and cancer patients with ICI-induced myocarditis. Deficiency of GSDME in male mice alleviates ICI-induced cardiac infiltration of T cells, macrophages, and monocytes, as well as mitochondrial damage and inflammation. Restoration of GSDME expression specifically in cardiomyocytes, rather than myeloid cells, in GSDME-deficient mice reproduces ICI-induced myocarditis. Mechanistically, quantitative proteomics reveal that GSDME-dependent pyroptosis promotes cell death and mitochondrial DNA release, which in turn activates cGAS-STING signaling, triggering a robust interferon response and myocardial immune/inflammation activation. Pharmacological blockade of GSDME attenuates ICI-induced myocarditis and improves long-term survival in mice. Our findings may advance the understanding of ICI-induced myocarditis and suggest that targeting the GSDME-cGAS-STING-interferon axis may help prevent and manage ICI-associated myocarditis.

A Narrative Review of the IL-18 and IL-37 Implications in the Pathogenesis of Atopic Dermatitis and Psoriasis: Prospective Treatment Targets

Atopic dermatitis and psoriasis are prevalent inflammatory skin conditions that significantly impact the quality of life of patients, with diverse treatment options available. Despite advances in understanding their underlying mechanisms, recent research highlights the significance of interleukins IL-18 and IL-37, in Th1, Th2, and Th17 inflammatory responses, closely associated with the pathogenesis of psoriasis and atopic dermatitis. Hence, IL-18 and IL-37 could potentially become therapeutic targets. This narrative review synthesizes knowledge on these interleukins, their roles in atopic dermatitis and psoriasis, and emerging treatment strategies. Findings of a literature search up to 30 May 2024, underscore a research gap in IL-37-targeted therapies. Conversely, IL-18-focused treatments have demonstrated promise in adult-onset Still's Disease, warranting further exploration for their potential efficacy in psoriasis and atopic dermatitis.

Genetic Approaches to Study Rheumatic Diseases and Its Implications in Clinical Practice

Patients with rare and complex rheumatic diseases (RDs) present with immense clinical variability inherent to all immunologic diseases. In addition to systemic and organ-specific inflammation, patients may display features of immunodeficiency or allergy, which may represent major diagnostic and therapeutic challenges. The person's genetic architecture has been a well-established risk factor for patients with RDs, albeit to variable degrees. Patients with early-onset diseases and/or positive family history (FH) have a strong genetic component, whereas patients with late-onset RDs demonstrate a more complex interplay of genetic and environmental risk factors. Overall, the genetic studies in patients with RDs have been instrumental to our understanding of innate and adaptive immunity in human health and disease. The elucidation of the molecular causes underlying rare diseases has played a major role in the identification of genes that are critical in the regulation of inflammatory responses. In addition, studies of patients with rare disorders may help determine the mechanisms of more complex autoimmune diseases by identifying variants with small effect sizes in the same genes. In contrast, studies of patients with common RDs are conducted in cohorts of patients with well-established phenotypes and ancestry-matched controls, and they aim to discover disease-related pathways that can inform the development of novel targeted therapies. Knowing the genetic cause of a disease has helped patients and families understand the disease progression and outcome. Here, we discuss the current understanding of genetic heritability and challenges in the diagnosis of RDs in patients and how this field may develop in the future.

Granzyme B-activated IL18 potentiates αβ and γδ CAR T cell immunotherapy in a tumor-dependent manner

Interleukin (IL)18 is a potent pro-inflammatory cytokine that is activated upon caspase 1 cleavage of the latent precursor, pro-IL18. Therapeutic T cell armoring with IL18 promotes autocrine stimulation and positive modulation of the tumor microenvironment (TME). However, existing strategies are imperfect since they involve constitutive/poorly regulated activity or fail to modify the TME. Here, we have substituted the caspase 1 cleavage site within pro-IL18 with that preferred by granzyme B, yielding GzB-IL18. We demonstrate that GzB-IL18 is constitutively released but remains functionally latent unless chimeric antigen receptor (CAR) T cells are activated, owing to concomitant granzyme B release. Armoring with GzB-IL18 enhances cytolytic activity, proliferation, interferon (IFN)-γ release, and anti-tumor efficacy by a similar magnitude to constitutively active IL18. We also demonstrate that GzB-IL18 provides a highly effective armoring strategy for γδ CAR T cells, leading to enhanced metabolic fitness and significant potentiation of therapeutic activity. Finally, we show that constitutively active IL18 can unmask CAR T cell-mediated cytokine release syndrome in immunocompetent mice. By contrast, GzB-IL18 promotes anti-tumor activity and myeloid cell re-programming without inducing such toxicity. Using this stringent system, we have tightly coupled the biological activity of IL18 to the activation state of the host CAR T cell, favoring safer clinical implementation of this technology.

The NLRP3 inflammasome is essential for IL-18 production in a murine model of macrophage activation syndrome

Hyperinflammatory disease is associated with an aberrant immune response resulting in cytokine storm. One such instance of hyperinflammatory disease is known as macrophage activation syndrome (MAS). The pathology of MAS can be characterised by significantly elevated serum levels of interleukin-18 (IL-18) and interferon gamma (IFNγ). Given the role for IL-18 in MAS, we sought to establish the role of inflammasomes in the disease process. Using a murine model of CpG-oligonucleotide-induced MAS, we discovered that the expression of the NLRP3 inflammasome was increased and correlated with IL-18 production. Inhibition of the NLRP3 inflammasome or the downstream caspase-1 prevented MAS-mediated upregulation of IL-18 in the plasma but, interestingly, did not alleviate key features of hyperinflammatory disease including hyperferritinaemia and splenomegaly. Furthermore blockade of IL-1 receptor with its antagonist IL-1Ra did not prevent the development of CpG-induced MAS, despite being clinically effective in the treatment of MAS. These data demonstrate that, during the development of MAS, the NLRP3 inflammasome was essential for the elevation in plasma IL-18 - a key cytokine in clinical cases of MAS - but was not a driving factor in the pathogenesis of CpG-induced MAS.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Inflammasomes in epithelial innate immunity: front line warriors

Our epithelium represents a battle ground against a variety of insults including pathogens and danger signals. It encodes multiple sensors that detect and respond to such insults, playing an essential role in maintaining and defending tissue homeostasis. One key set of defense mechanisms is our inflammasomes which drive innate immune responses including, sensing and responding to pathogen attack, through the secretion of pro-inflammatory cytokines and cell death. Identification of physiologically relevant triggers for inflammasomes has greatly influenced our ability to decipher the mechanisms behind inflammasome activation. Furthermore, identification of patient mutations within inflammasome components implicates their involvement in a range of epithelial diseases. This review will focus on exploring the roles of inflammasomes in epithelial immunity and cover: the diversity and differential expression of inflammasome sensors amongst our epithelial barriers, their ability to sense local infection and damage and the contribution of the inflammasomes to epithelial homeostasis and disease.

Heterogeneity of macrophage activation syndrome and treatment progression

Macrophage activation syndrome (MAS) is a rare complication of autoimmune inflammatory rheumatic diseases (AIIRD) characterized by a progressive and life-threatening condition with features including cytokine storm and hemophagocytosis. Predisposing factors are typically associated with microbial infections, genetic factors (distinct from typical genetically related hemophagocytic lymphohistiocytosis (HLH)), and inappropriate immune system overactivation. Clinical features include unremitting fever, generalized rash, hepatosplenomegaly, lymphadenopathy, anemia, worsening liver function, and neurological involvement. MAS can occur in various AIIRDs, including but not limited to systemic juvenile idiopathic arthritis (sJIA), adult-onset Still's disease (AOSD), systemic lupus erythematosus (SLE), Kawasaki disease (KD), juvenile dermatomyositis (JDM), rheumatoid arthritis (RA), and Sjögren's syndrome (SS), etc. Although progress has been made in understanding the pathogenesis and treatment of MAS, it is important to recognize the differences between different diseases and the various treatment options available. This article summarizes the cell types and cytokines involved in MAS-related diseases, the heterogeneity, and treatment options, while also comparing it to genetically related HLH.

Human NLRC4 expression promotes cancer survival and associates with type I interferon signaling and immune infiltration

The immune system can control cancer progression. However, even though some innate immune sensors of cellular stress are expressed intrinsically in epithelial cells, their potential role in cancer aggressiveness and subsequent overall survival in humans is mainly unknown. Here, we show that nucleotide-binding oligomerization domain-like receptor (NLR) family CARD domain-containing 4 (NLRC4) is downregulated in epithelial tumor cells of patients with colorectal cancer (CRC) by using spatial tissue imaging. Strikingly, only the loss of tumor NLRC4, but not stromal NLRC4, was associated with poor immune infiltration (mainly DCs and CD4+ and CD8+ T cells) and accurately predicted progression to metastatic stage IV and decrease in overall survival. By combining multiomics approaches, we show that restoring NLRC4 expression in human CRC cells triggered a broad inflammasome-independent immune reprogramming consisting of type I interferon (IFN) signaling genes and the release of chemokines and myeloid growth factors involved in the tumor infiltration and activation of DCs and T cells. Consistently, such reprogramming in cancer cells was sufficient to directly induce maturation of human DCs toward a Th1 antitumor immune response through IL-12 production in vitro. In multiple human carcinomas (colorectal, lung, and skin), we confirmed that NLRC4 expression in patient tumors was strongly associated with type I IFN genes, immune infiltrates, and high microsatellite instability. Thus, we shed light on the epithelial innate immune sensor NLRC4 as a therapeutic target to promote an efficient antitumor immune response against the aggressiveness of various carcinomas.

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.

Hidradenitis Suppurativa-Related Autoinflammatory Syndromes: An Updated Review on the Clinics, Genetics, and Treatment of Pyoderma gangrenosum, Acne and Suppurative Hidradenitis (PASH), Pyogenic Arthritis, Pyoderma gangrenosum, Acne and Suppurative Hidradenitis (PAPASH), Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis (SAPHO), and Rarer Forms

Hidradenitis suppurativa (HS) is an autoinflammatory skin disorder of the terminal hair follicle, which can present in sporadic, familial, or syndromic form. A classification has been proposed for the latter, distinguishing cases associated with a known genetic condition, with follicular keratinization disorders or with autoinflammatory diseases. This review focuses on the clinical and genetic features of those entities (ie, pyoderma gangrenosum [PG], acne and HS; PG, acne, pyogenic arthritis and HS; psoriatic arthritis, PG, acne and HS; synovitis, acne, pustulosis, hyperostosis, osteitis; and so forth) for which the collective term HS-related autoinflammatory syndromes is proposed.

Cytokine Storm Syndrome Responsive to IL-1 Inhibition in Trisomy 21

Background

Cytokine storm syndromes (CSS) are life-threatening systemic inflammatory disorders caused by immune system dysregulation. They can lead to organ failure and are triggered by various factors, including infections, malignancy, inborn errors of immunity, and autoimmune conditions. Trisomy 21 (TS21), also known as Down syndrome, is a genetic disorder associated with immune dysfunction, increased infection susceptibility, and inflammation. While TS21 has been linked to infectious-triggered hyperinflammation, its role as a primary cause of CSS has not been confirmed. Case Presentation. We present a case of a 16-year-old male with TS21 with fever, rash, joint pain, and abdominal symptoms. Extensive investigations ruled out infections, autoimmune conditions, malignancies, and inborn errors of immunity as triggers for a CSS. The patient's symptoms improved with treatment using IL-1 inhibition and corticosteroids.

Conclusions

This case reinforces that TS21 is an immune dysregulation disorder and highlights the importance of considering CSS in TS21 patients, even when triggers are unclear. The positive response to IL-1 inhibition in this patient suggests that dysregulation of the IL-1 superfamily and the NLRP3 inflammasome may contribute to CSS in TS21. This finding raises the possibility of using IL-1 inhibition as a treatment approach for CSS in TS21 patients.

LRRK2 G2019S Promotes Colon Cancer Potentially via LRRK2-GSDMD Axis-Mediated Gut Inflammation

Leucine-rich repeat kinase 2 (LRRK2) is a serine-threonine protein kinase belonging to the ROCO protein family. Within the kinase domain of LRRK2, a point mutation known as LRRK2 G2019S has emerged as the most prevalent variant associated with Parkinson's disease. Recent clinical studies have indicated that G2019S carriers have an elevated risk of cancers, including colon cancer. Despite this observation, the underlying mechanisms linking LRRK2 G2019S to colon cancer remain elusive. In this study, employing a colitis-associated cancer (CAC) model and LRRK2 G2019S knock-in (KI) mouse model, we demonstrate that LRRK2 G2019S promotes the pathogenesis of colon cancer, characterized by increased tumor number and size in KI mice. Furthermore, LRRK2 G2019S enhances intestinal epithelial cell proliferation and inflammation within the tumor microenvironment. Mechanistically, KI mice exhibit heightened susceptibility to DSS-induced colitis, with inhibition of LRRK2 kinase activity ameliorating colitis severity and CAC progression. Our investigation also reveals that LRRK2 G2019S promotes inflammasome activation and exacerbates gut epithelium necrosis in the colitis model. Notably, GSDMD inhibitors attenuate colitis in LRRK2 G2019S KI mice. Taken together, our findings offer experimental evidence indicating that the gain-of-kinase activity in LRRK2 promotes colorectal tumorigenesis, suggesting LRRK2 as a potential therapeutic target in colon cancer patients exhibiting hyper LRRK2 kinase activity.

Identification of miRNAs that target Fcγ receptor-mediated phagocytosis during macrophage activation syndrome

Macrophage activation syndrome (MAS) is a life-threatening complication of systemic juvenile arthritis, accompanied by cytokine storm and hemophagocytosis. In addition, COVID-19-related hyperinflammation shares clinical features of MAS. Mechanisms that activate macrophages in MAS remain unclear. Here, we identify the role of miRNA in increased phagocytosis and interleukin-12 (IL-12) production by macrophages in a murine model of MAS. MAS significantly increased F4/80+ macrophages and phagocytosis in the mouse liver. Gene expression profile revealed the induction of Fcγ receptor-mediated phagocytosis (FGRP) and IL-12 production in the liver. Phagocytosis pathways such as High-affinity IgE receptor is known as Fc epsilon RI -signaling and pattern recognition receptors involved in the recognition of bacteria and viruses and phagosome formation were also significantly upregulated. In MAS, miR-136-5p and miR-501-3p targeted and caused increased expression of Fcgr3, Fcgr4, and Fcgr1 genes in FGRP pathway and consequent increase in phagocytosis by macrophages, whereas miR-129-1-3p and miR-150-3p targeted and induced Il-12. Transcriptome analysis of patients with MAS revealed the upregulation of FGRP and FCGR gene expression. A target analysis of gene expression data from a patient with MAS discovered that miR-136-5p targets FCGR2A and FCGR3A/3B, the human orthologs of mouse Fcgr3 and Fcgr4, and miR-501-3p targets FCGR1A, the human ortholog of mouse Fcgr1. Together, we demonstrate the novel role of miRNAs during MAS pathogenesis, thereby suggesting miRNA mimic-based therapy to control the hyperactivation of macrophages in patients with MAS as well as use overexpression of FCGR genes as a marker for MAS classification.

The NLRP3 inflammasome is essential for IL-18 production in a murine model of macrophage activation syndrome

Hyperinflammatory disease is associated with an aberrant immune response resulting in cytokine storm. One such instance of hyperinflammatory disease is known as macrophage activation syndrome (MAS). The pathology of MAS can be characterised by significantly elevated serum levels of interleukin (IL)-18 and interferon (IFN)-γ. Given the role for IL-18 in MAS, we sought to establish the role of inflammasomes in the disease process. Using a murine model of CpG-DNA induced MAS, we discovered that the expression of the NLRP3 inflammasome was increased and correlated with IL-18 production. Inhibition of the NLRP3 inflammasome, or downstream caspase-1, prevented MAS-mediated upregulation of plasma IL-18 but interestingly did not alleviate key features of hyperinflammatory disease including hyperferritinaemia and splenomegaly. Furthermore IL-1 receptor blockade with IL-1Ra did not prevent the development of CpG-induced MAS, despite being clinically effective in the treatment of MAS. These data demonstrate that in the development of MAS, the NLRP3 inflammasome was essential for the elevation in plasma IL-18, a key cytokine in clinical cases of MAS, but was not a driving factor in the pathogenesis of CpG-induced MAS.

Late Onset of Primary Hemophagocytic Lymphohistiocytosis (HLH) with a Novel Constellation of Compound Heterozygosity Involving Two Missense Variants in the PRF1 Gene

Hemophagocytic lymphohistiocytosis (HLH) is a rare but in most cases life-threatening immune-mediated disease of the hematopoietic system frequently associated with hematologic neoplasms. Here, we report on a case in which we detected a novel constellation of two missense variants affecting the PRF1 gene, leading to de novo primary HLH. Diagnostics included a comprehensive clinical work-up and standard methods of hematopathology as well as extended molecular genomics based on polymerase chain reaction (PCR) reactions and the calculation of three-dimensional molecule reconstructions of PRF1. Subsequently, a comprehensive review of the literature was performed, which showed that this compound heterozygosity has not been previously described. The patient was a 20-year-old female. Molecular diagnostics revealed two heterozygous missense variants in the PRF1 gene (A91V and R104C) on exon 2. Apart from the finding of two inconclusive genetic variants, all clinical criteria defined by the HLH study group of Histiocyte Society were met at initial presentation. The final diagnosis was made in cooperation with the Consortium of German HLH-reference centers. Here, chemotherapy did not lead to sufficient sustained disease control. Therefore, the decision for allogenic hematopoietic stem cell transplantation (alloHSCT) was made. Hitherto, the duration of response was 6 months. Due to severe and unmanageable hepatic graft-versus-host disease (GvHD), the patient died. We report on a novel constellation of a compound heterozygosity containing two missense variants on exon 2 of the PRF1 gene. To the authors' best knowledge, this is the first presentation of a primary HLH case harboring this genomic constellation with late-onset clinical manifestation.