IntroductionColorectal cancer (CRC) is a prevalent malignancy with significant morbidity and mortality worldwide. A deeper understanding of the interaction of cancer cells with other cells in the tumor microenvironment is crucial to devise effective therapeutic strategies. MUC2, a major component of the protective mucus layer in the gastrointestinal tract, has been implicated in CRC progression and immune response regulation.MethodIn this study, we sought to elucidate the relationship between MUC2 expression and immune infiltration within CRC using in vitro models involving two well-established cell lines, HT-29 and LS-174T. By employing CRISPR-mediated MUC2 knockout, we investigated the influence of MUC2 on tumor immune infiltration and its interplay with T cells and NK cells enriched peripheral blood mononuclear cells (PBMCs) in 3D spheroid cultures.ResultsWhile MUC2 was more abundant in LS-174T cell line compared to HT-29, its knockout resulted in increased immune infiltration solely in the HT-29 cell line, but not in the LS-174T cell line. We revealed that the removal of MUC2 protein was compensated in LS-174T by the expression of other gel-forming mucin proteins (MUC6, MUC5B) commonly expressed in the gastrointestinal epithelium, while this was not observed in HT-29 cell line.ConclusionOur study is the first to demonstrate that MUC2 functions as a physical barrier to immune infiltration in colorectal cancer (CRC) in vitro. In HT-29 cells, MUC2 knockout increased immune infiltration, while in LS-174T cells, compensatory expression of other mucins (MUC6, MUC5B) maintained the barrier. These findings reveal the complexity of mucin biology in CRC and suggest that targeting mucin pathways could be a novel therapeutic approach.

Purpose PI4KA-related disorder is a highly clinically variable condition characterized by neurological (limb spasticity, developmental delay, intellectual disability, seizures, ataxia, nystagmus) and gastrointestinal (inflammatory bowel disease and multiple intestinal atresia) manifestations. Although features consistent with immunodeficiency (autoimmunity/autoinflammation and recurrent infections) have been reported in a subset of patients, the burden of B-cell deficiency and hypogammaglobulinemia has not been extensively investigated. We sought to describe the clinical presentation and manifestations of patients with PI4KA-related disorder and to investigate the metabolic consequences of biallelic PI4KA variants in B cells. Methods Clinical data from patients with PI4KA variants were obtained. Multi-omics analyses combining transcriptome, proteome, lipidome and metabolome analyses in conjunction with functional assays were performed in EBV-transformed B cells. Results Clinical and laboratory data of 13 patients were collected. Recurrent infections (7/13), autoimmune/autoinflammatory manifestations (5/13), B-cell deficiency (8/13) and hypogammaglobulinemia (8/13) were frequently observed. Patients' B cells frequently showed increased transitional and decreased switched memory B-cell subsets. Pathway analyses based on differentially expressed transcripts and proteins confirmed the central role of PI4KA in B cell differentiation with altered B-cell receptor (BCR) complex and signalling. By altering lipids production and tricarboxylic acid cycle regulation, and causing increased endoplasmic reticulum stress, biallelic PI4KA mutations disrupt B cell metabolism inducing mitochondrial dysfunction. As a result, B cells show hyperactive PI3K/mTOR pathway, increased autophagy and deranged cytoskeleton organization. Conclusion By altering lipid metabolism and TCA cycle, impairing mitochondrial activity, hyperactivating mTOR pathway and increasing autophagy, PI4KA-related disorder causes a syndromic inborn error of immunity presenting with B-cell deficiency and hypogammaglobulinemia.

Autophagy is a fundamental and evolutionary conserved biological pathway with vital roles in intracellular quality control and homeostasis. The process of autophagy involves the engulfment of intracellular targets by autophagosomes and their delivery to the lysosome for digestion and recycling. We have previously reported recessive variants in EPG5, encoding for the ectopic P-granules 5 autophagy protein with a crucial role in autophagosome-lysosome fusion, as the cause of Vici syndrome (VS), a severe multisystem neurodevelopmental disorder defined by a combination of distinct clinical features including callosal agenesis, cataracts, cardiomyopathy, immunodeficiency, and hypopigmentation. Here, we present extensive novel genetic, clinical, neuroradiological and pathological features from the largest cohort of EPG5-related disorders reported to date, complemented by experimental findings from patient cells and models of EPG5 defects in Caenorhabditis elegans and Mus musculus. We identified 200 patients with recessive EPG5 variants, 86 of them previously unpublished. The associated phenotypic spectrum ranged from antenatally lethal presentations and the classic VS phenotype (n=60) to much milder neurodevelopmental disorders with less specific manifestations (n=140). Myopathic features and epilepsy with variable progression were frequently observed. Novel manifestations included early-onset parkinsonism and dystonia with cognitive decline during adolescence, hereditary spastic paraplegia (HSPP), and myoclonus. Radiological findings included previously recognized EPG5-related features with callosal abnormalities and pontocerebellar hypoplasia, and a range of novel features suggesting an emerging continuum with disorders of brain iron accumulation or copper metabolism as well as HSPPs. Genotype-phenotype studies suggested a correlation between predicted residual EPG5 expression and clinical severity, especially regarding disease progression and survival. The Epg5 p.Gln331Arg knock-in mouse, a model of milder EPG5-related disorders, showed an age-related motor phenotype and impaired autophagic clearance in several brain regions mirroring those also affected in humans. In Caenorhabditis elegans, epg-5 knockdown gave rise to neurodevelopmental features and motor impairment comparable to defects in parkinsonism-related genes, abnormal mitochondrial respiration, and impaired mitophagic clearance early in life. Cellular assays revealed impaired PINK1-Parkin dependent mitophagic clearance in patient fibroblasts. Our findings expand the phenotypic spectrum of EPG5-related disorders and indicate a life time continuum of disease that overlaps with other disorders of defective autophagy and intracellular trafficking. Our observations also suggest close links between early-onset neurodevelopmental and neurodegenerative conditions of later onset due to EPG5 defects, in particular dystonia and parkinsonism, highlighting the fundamental importance of dysfunctional autophagy in the pathophysiology of common neurodegenerative disorders.### Competing Interest StatementThe authors have declared no competing interest.### Funding StatementThis work was supported by grants from the European Union Horizon 2020 Programme (765912 DRIVE H2020-MSCA-ITN-2017) to CD, MF and HJ, Action Medical Research (2446) to HJ and MF, and Action Medical Research (GN2959) to KS and MRD. HSD was supported by the Koeln Fortune Program/Faculty of Medicine, University of Cologne (371/2021 and 243/2022), as well as the Cologne Clinician Scientist Program/Medical Faculty/University of Cologne and German Research Foundation (CCSP, DFG project No. 413543196). AA was supported by the Max Planck Gesellschaft. TSB was supported by the Netherlands Organisation for Scientific Research (ZonMw Vidi, grant 09150172110002), and acknowledges ongoing support from EpilepsieNL and CURE Epilepsy. KO is supported by Estonian Research Council grant PRG2040. Funding bodies did not have any influence on study design, results, and data interpretation or final manuscript.### Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:IRB of Medical Faculty, University of Cologne gave ethical approval for this work.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors.

PURPOSE:Lipopolysaccharide-responsive beige-like anchor protein (LRBA) encodes a widely expressed cytosolic protein that participates in polarized vesicle trafficking. Homozygous loss-of-function LRBA mutations can lead to immune deficiency due to the lack of immune regulation, classified as a part of Tregopathies. We present a case of a 49-year-old female, with polyarthralgia in metacarpophalangeal and proximal interphalangeal joints bilaterally, and morning stiffness, leading to the diagnosis of rheumatoid arthritis treated with pulse steroid therapy. She had experienced sepsis and in-depth scrutiny revealed panhypogammaglobulinemia. After being referred to the immunology clinic, she was followed under the diagnosis of common variable immunodeficiency (CVID)-like inborn errors of immunity (IEI). METHODS AND RESULTS:Physical examination and diagnostic follow-up revealed massive splenomegaly accompanied by portal hypertension, and ulcerations in the colon. She also presented with periodic hematuria and dysuria. Cystoscopic biopsy revealed mast cell-derived interstitial cystitis which has not been previously reported in LRBA deficiency in the literature to our knowledge. A multi-gene next-generation sequencing panel performed for immune deficiencies (264 genes and 524 amplicons), resulted in the identification of an apparently homozygous LRBA mutation (p.Arg722His) in the Beige and Chediak-Higashi (BEACH) domain. The SNP array showed copy neutral absence of heterozygosity of the entire chromosome 4, which is consistent with uniparental isodisomy of chromosome 4. CONCLUSION:In conclusion, this case study underscores the critical role of LRBA in immune regulation and highlights the clinical heterogeneity associated with LRBA deficiency. The patient's presentation with severe immune dysregulation, including massive splenomegaly, portal hypertension, and the novel finding of mast cell-derived interstitial cystitis, expands the clinical spectrum of LRBA mutations. The identification of an apparently homozygous LRBA mutation via next-generation sequencing further emphasizes the importance of genetic analysis in diagnosing monogenic defects manifested as CVID-like phenotype. This is the first reported case of LRBA deficiency due to whole chromosome UPD to our knowledge. Future research should focus on elucidating the full range of clinical manifestations and developing targeted therapies for patients with LRBA deficiency.

Inflammatory bowel diseases (IBD) encompass a group of chronic inflammatory disorders primarily impacting the gastrointestinal system, and they may also affect other organ systems.While common forms of IBD typically arise from multifactorial causes, there exists a subset of patients with single gene defects known as monogenic IBD (mIBD).Over 100 genes have been associated with mIBD, spanning various biological pathways which affect various tissues; the immune system is the most commonly involved, but more rarely, the intestinal epithelium is the primarily affected compartment.Timely diagnosis hinges on awareness and the application of contemporary molecular techniques.Due to the diverse range of causes, managing mIBD requires a multidisciplinary approach.Conventional treatments often fall short, necessitating a personalized strategy that considers the multifaceted nature of mIBD presentations and the diverse etiologic factors.In recent times, novel therapies have emerged, targeting specific causative genes or affected pathways.This discussion delves into the fundamental aspects of mIBD, with particular emphasis on recent breakthroughs in the field, encompassing newly identified gene defects and innovative management strategies.

The interleukin-7 receptor (IL-7R) is primarily expressed on lymphoid cells and plays a crucial role in the development, proliferation, and survival of T cells. Autosomal recessive mutations that disrupt IL-7Rα chain expression give rise to a severe combined immunodeficiency (SCID), which is characterized by lymphopenia and a T−B+NK+ phenotype. The objective here was to diagnose two siblings displaying the T−B+NK+ SCID phenotype as initial clinical genetic testing did not detect any variants in known SCID genes. Whole genome sequencing (WGS) was utilized to identify potential variants causing the SCID phenotype. Splicing prediction tools were employed to assess the deleterious impact of the mutation. Polymerase Chain Reaction (PCR), Sanger sequencing, flow cytometry, and ELISA were then used to validate the pathogenicity of the detected mutation. We discovered a novel homozygous synonymous mutation in the IL7R gene. Our functional studies indicate that this variant is pathogenic, causing exon 6, which encodes the transmembrane domain, to be preferentially spliced out. In this study, we identified a novel rare synonymous mutation causing a loss of IL-7Rα expression at the cellular membrane. This case demonstrates the value of reanalyzing genetic data based on the clinical phenotype and highlights the significance of functional studies in determining the pathogenicity of genetic variants.

Background Genome sequencing of large biobanks from under-represented ancestries provides a valuable resource for the interrogation of Mendelian disease burden at world population level, complementing small-scale familial studies. Methods Here, we interrogate 6045 whole genomes from Qatar-a Middle Eastern population with high consanguinity and understudied mutational burden-enrolled at the national Biobank and phenotyped for 58 clinically-relevant quantitative traits. We examine a curated set of 2648 Mendelian genes from 20 panels, annotating known and novel pathogenic variants and assessing their penetrance and impact on the measured traits. Results We find that 62.5% of participants are carriers of at least 1 known pathogenic variant relating to recessive conditions, with homozygosity observed in 1 in 150 subjects (0.6%) for which Peninsular Arabs are particularly enriched versus other ancestries (5.8-fold). On average, 52.3 loss-of-function variants were found per genome, 6.5 of which affect a known Mendelian gene. Several variants annotated in ClinVar/HGMD as pathogenic appeared at intermediate frequencies in this cohort (1-3%), highlighting Arab founder effect, while others have exceedingly high frequencies (> 5%) prompting reconsideration as benign. Furthermore, cumulative gene burden analysis revealed 56 genes having gene carrier frequency > 1/50, including 5 ACMG Tier 3 panel genes which would be candidates for adding to newborn screening in the country. Additionally, leveraging 58 biobank traits, we systematically assess the impact of novel/rare variants on phenotypes and discover 39 candidate large-effect variants associating with extreme quantitative traits. Furthermore, through rare variant burden testing, we discover 13 genes with high mutational load, including 5 with impact on traits relevant to disease conditions, including metabolic disorder and type 2 diabetes, consistent with the high prevalence of these conditions in the region. Conclusions This study on the first phase of the growing Qatar Genome Program cohort provides a comprehensive resource from a Middle Eastern population to understand the global mutational burden in Mendelian genes and their impact on traits in seemingly healthy individuals in high consanguinity settings.

BACKGROUND:TRPM4 is a broadly expressed, calcium-activated, monovalent cation channel that regulates immune cell function in mice and cell lines. Clinically, however, partial loss- or gain-of-function mutations in TRPM4 lead to arrhythmia and heart disease, with no documentation of immunologic disorders.OBJECTIVE:To characterize functional cellular mechanisms underlying the immune dysregulation phenotype in a proband with a mutated TRPM4 gene.METHODS:We employed a combination of biochemical, cell biological, imaging, omics analyses, flow cytometry, and gene editing approaches.RESULTS:We report the first human cases to our knowledge with complete loss of the TRPM4 channel, leading to immune dysregulation with frequent bacterial and fungal infections. Single-cell and bulk RNA sequencing point to altered expression of genes affecting cell migration, specifically in monocytes. Inhibition of TRPM4 in T cells and the THP-1 monocyte cell line reduces migration. More importantly, primary T cells and monocytes from TRPM4 patients migrate poorly. Finally, CRISPR knockout of TRPM4 in THP-1 cells greatly reduces their migration potential.CONCLUSION:Our results demonstrate that TRPM4 plays a critical role in regulating immune cell migration, leading to increased susceptibility to infections.

Owing to advances in genomics that enable differentiation of molecular aetiologies, patients with monogenic inflammatory bowel disease (mIBD) potentially have access to genotype-guided precision medicine. In this Expert Recommendation, we review the therapeutic research landscape of mIBD, the reported response to therapies, the medication-related risks and systematic bias in reporting. The mIBD field is characterized by the absence of randomized controlled trials and is dominated by retrospective observational data based on case series and case reports. More than 25 off-label therapeutics (including small-molecule inhibitors and biologics) as well as cellular therapies (including haematopoietic stem cell transplantation and gene therapy) have been reported. Heterogeneous reporting of outcomes impedes the generation of robust therapeutic evidence as the basis for clinical decision making in mIBD. We discuss therapeutic goals in mIBD and recommend standardized reporting (mIBD REPORT (monogenic Inflammatory Bowel Disease Report Extended Phenotype and Outcome of Treatments) standards) to stratify patients according to a genetic diagnosis and phenotype, to assess treatment effects and to record safety signals. Implementation of these pragmatic standards should help clinicians to assess the therapy responses of individual patients in clinical practice and improve comparability between observational retrospective studies and controlled prospective trials, supporting future meta-analysis. In this Expert Recommendation, Uhlig and colleagues review the therapeutic landscape for monogenic inflammatory bowel disease and propose recommendations for standardized reporting of clinical outcomes.

Actin-related protein 2/3 complex subunit 1B (ARPC1B) is involved in the control of actin polymerization. Homozygous loss-of-function mutations in ARPC1B cause immunodeficiency 71 classified as the syndromic combined immunodeficiency with congenital thrombocytopenia. Here we describe two siblings presented with homozygous mutations in the ARPC1B gene. Patient 1, a 12-year-old male, presented with bloody diarrhea, vomiting, fever and eczema starting at the age of five months. GIS endoscopic examination was compatible with Chron’s Disease. He had repeated hospitalizations due to fever, bloody diarrhea, vomiting, pneumonia, asthma, and bronchiolitis. Physical examination was normal except for marked growth retardation. Complete blood count (CBC) revealed thrombocytopenia with normal MPV values, lymphopenia as well as eosinophilia. He had high Ig A, low Ig M, and normal Ig G and Ig E levels. In the lymphocyte subgroup analysis, CD3+, CD8+ T, CD 19+ B cell and RTE percentages were low, and CD21+38+ low B cell percentages were high. Lymphocyte proliferation and Treg cell analysis were normal compared to healthy controls. Patient 2, Patient 1’s three-year-old brother started to complain of vomiting, bloody diarrhea, and eczema when he was four days old. Colonoscopy was revelaed Crohn’s Disease. He had episodes of wheezing and repeated hospitalizations for bronchiolitis. Physical examination revealed growth retardation and severe eczema. CBC was normal except for intermittent leukocytosis and eosinophilia. He had high Ig A and Ig E, low Ig M, and normal Ig G levels. In lymphocyte subgroup analysis, CD3 + T cell, RTE, naive, and CSM B cell percentages were low, CD21+38+ low B and Exhausted Cd8+ T cell percentages were high. T cell proliferative response was significantly lower than that in healthy controls. Treg cell analysis was also found to be significantly lower.

Background: Toll-like receptors (TLRs) mediate functions for host defense and inflammatory responses. TLR4 recognizes LPS, a component of gram-negative bacteria as well as host -derived endogenous ligands such as S100A8 and S100A9 proteins. Objective: We sought to report phenotype and cellular function of individuals with complete TLR4 deficiency.Methods: We performed genome sequencing and investigated exome and genome sequencing databases. Cellular responses were studied on primary monocytes, macrophages, and neutrophils, as well as cell lines using flow cytometry, reporter, and cytokine assays. Results: We identified 2 individuals in a family of Qatari origin carrying a homozygous stop codon variant p.Q188X in TLR4 presenting with a variable phenotype (asymptomatic and inflammatory bowel disease consistent with severe perianal Crohn disease). A third individual with homozygous p.Y794X was identified in a population database. In contrast to hypomorphic polymorphisms p.D299G and p.T399I, the variants p.Q188X and p.Y794X completely abrogated LPS-induced cytokine responses whereas TLR2 response was normal. TLR4 deficiency causes a neutrophil CD62L shedding defect, whereas antimicrobial activity toward intracellular Salmonella was intact. Conclusions: Biallelic TLR4 deficiency in humans causes an inborn error of immunity in responding to LPS. This complements the spectrum of known primary immunodeficiencies, in particular myeloid differentiation primary response 88 (MYD88) or the IL-1 receptor-associated kinase 4 (IRAK4) deficiency that are downstream of TLR4 and TLR2 signaling. (J Allergy Clin Immunol 2023;151:783-90.)

BACKGROUND:Lipopolysaccharide-responsive beige-like anchor protein (LRBA) deficiency and cytotoxic T-lymphocyte protein-4 (CTLA-4) insufficiency are recently described disorders that present with susceptibility to infections, autoimmunity, and lymphoproliferation. Clinical and immunological comparisons of the diseases with long-term follow-up have not been previously reported. We sought to compare the clinical and laboratory manifestations of both diseases and investigate the role of flow cytometry in predicting the genetic defect in patients with LRBA deficiency and CTLA-4 insufficiency.METHODS:Patients were evaluated clinically with laboratory assessments for lymphocyte subsets, T follicular helper cells (TFH ), LRBA expression, and expression of CD25, FOXP3, and CTLA4 in regulatory T cells (Tregs) at baseline and 16 h post-stimulation.RESULTS:LRBA-deficient patients (n = 29) showed significantly early age of symptom onset, higher rates of pneumonia, autoimmunity, chronic diarrhea, and failure to thrive compared to CTLA-4 insufficiency (n = 12). In total, 29 patients received abatacept with favorable responses and the overall survival probability was not different between transplanted versus non-transplanted patients in LRBA deficiency. Meanwhile, higher probability of survival was observed in CTLA-4-insufficient patients (p = 0.04). The T-cell subsets showed more deviation to memory cells in CTLA-4-insufficiency, accompanied by low percentages of Treg and dysregulated cTFH cells response in both diseases. Cumulative numbers of autoimmunities positively correlated with cTFH frequencies. Baseline CTLA-4 expression was significantly diminished in LRBA deficiency and CTLA-4 insufficiency, but significant induction in CTLA-4 was observed after short-term T-cell stimulation in LRBA deficiency and controls, while this elevation was less in CTLA-4 insufficiency, allowing to differentiate this disease from LRBA deficiency with high sensitivity (87.5%) and specificity (90%).CONCLUSION:This cohort provided detailed clinical and laboratory comparisons for LRBA deficiency and CTLA-4 insufficiency. The flow cytometric approach is useful in predicting the defective gene; thus, targeted sequencing can be conducted to provide rapid diagnosis and treatment for these diseases impacting the CTLA-4 pathway.

Epilepsy is one of the most common neurological disorders. The cost to the health system and the impact on quality of life for patients with intractable epilepsies and associated comorbidities is significant. Disease etiology and pathogenesis are still not well understood. Genetic mutations have been shown to be associated with 70% of epilepsies, with the majority being non-monogenic, and the remaining 30% enigmatic. This knowledge gap necessitates further research. The goal of this study is to partially bridge this gap through the genetic analysis of a cohort of patients with epilepsy from an understudied and highly consanguineous population, primarily of ethnicities from the Middle East and North Africa region. Whole exome sequencing was carried out in 81 patients with epilepsy and their family members at a tertiary center in Qatar. We used the data to identify pathogenic variants and type HLA alleles for 13 class I & II genes. We associated the resulting alleles with disease status, using controls of a closely related ethnicity. The genetic yield was approximately 22% for known epilepsy genes. We also suggest a list of 20 genes that could be culprits. Analysis of the biological pathways in which these genes are involved show that focal and generalized epilepsy genes are highly interwound. HLA analysis revealed that class II HLA genes are associated with disease status, particularly DRB4*03:01N, which plays a strong protective role. Our findings suggest that an immune etiology may contribute to the disease together with a genetic culprit, emphasizing the complexity of the etiology of the disease.

We report a pleiotropic disease due to loss-of-function mutations in RHBDF2, the gene encoding iRHOM2, in two kindreds with recurrent infections in different organs. One patient had recurrent pneumonia but no colon involvement, another had recurrent infectious hemorrhagic colitis but no lung involvement and the other two experienced recurrent respiratory infections. Loss of iRHOM2, a rhomboid superfamily member that regulates the ADAM17 metalloproteinase, caused defective ADAM17-dependent cleavage and release of cytokines, including tumor-necrosis factor and amphiregulin. To understand the diverse clinical phenotypes, we challenged Rhbdf2−/− mice with Pseudomonas aeruginosa by nasal gavage and observed more severe pneumonia, whereas infection with Citrobacter rodentium caused worse inflammatory colitis than in wild-type mice. The fecal microbiota in the colitis patient had characteristic oral species that can predispose to colitis. Thus, a human immunodeficiency arising from iRHOM2 deficiency causes divergent disease phenotypes that can involve the local microbial environment. Kubo et al. report two kindreds that exhibit a deficiency of iRHOM2, which interacts with ADAM17, leading to defective release of TNF and CD62L and resulting in altered immune responses to opportunistic infections.

Maturity-onset diabetes of the young, MODY, is an autosomal dominant disease with incomplete penetrance. In a family with multiple generations of diabetes and several early onset diabetic siblings, we found the previously reported P33T PDX1 damaging mutation. Interestingly, this substitution was also present in a healthy sibling. In contrast, a second very rare heterozygous damaging mutation in the necroptosis terminal effector, MLKL, was found exclusively in the diabetic family members. Aberrant cell death by necroptosis is a cause of inflammatory diseases and has been widely implicated in human pathologies, but has not yet been attributed functions in diabetes. Here, we report that the MLKL substitution observed in diabetic patients, G316D, results in diminished phosphorylation by its upstream activator, the RIPK3 kinase, and no capacity to reconstitute necroptosis in two distinct MLKL −/− human cell lines. This MLKL mutation may act as a modifier to the P33T PDX1 mutation, and points to a potential role of impairment of necroptosis in diabetes. Our findings highlight the importance of family studies in unraveling MODY’s incomplete penetrance, and provide further support for the involvement of dysregulated necroptosis in human disease.

BACKGROUND:Biallelic loss-of-function mutations in CARMIL2 cause combined immunodeficiency associated with dermatitis, inflammatory bowel disease (IBD), and EBV-related smooth muscle tumors. Clinical and immunological characterizations of the disease with long-term follow-up and treatment options have not been previously reported in large cohorts. We sought to determine the clinical and immunological features of CARMIL2 deficiency and long-term efficacy of treatment in controlling different disease manifestations.METHODS:The presenting phenotypes, long-term outcomes, and treatment responses were evaluated prospectively in 15 CARMIL2-deficient patients, including 13 novel cases. Lymphocyte subpopulations, protein expression, regulatory T (Treg), and circulating T follicular helper (cTFH ) cells were analyzed. Three-dimensional (3D) migration assay was performed to determine T-cell shape.RESULTS:Mean age at disease onset was 38 ± 23 months. Main clinical features were skin manifestations (n = 14, 93%), failure to thrive (n = 10, 67%), recurrent infections (n = 10, 67%), allergic symptoms (n = 8, 53%), chronic diarrhea (n = 4, 27%), and EBV-related leiomyoma (n = 2, 13%). Skin manifestations ranged from atopic and seborrheic dermatitis to psoriasiform rash. Patients had reduced proportions of memory CD4+ T cells, Treg, and cTFH cells. Memory B and NK cells were also decreased. CARMIL2-deficient T cells exhibited reduced T-cell proliferation and cytokine production following CD28 co-stimulation and normal morphology when migrating in a high-density 3D collagen gel matrix. IBD was the most severe clinical manifestation, leading to growth retardation, requiring multiple interventional treatments. All patients were alive with a median follow-up of 10.8 years (range: 3-17 years).CONCLUSION:This cohort provides clinical and immunological features and long-term follow-up of different manifestations of CARMIL2 deficiency.

MAIT cells have been shown to be activated upon several viral infections in a TCR-independent manner by responding to inflammatory cytokines secreted by antigen-presenting cells. Recently, a few studies have shown a similar activation of MAIT cells in response to severe acute respiratory coronavirus 2 (SARS-CoV-2) infection. In this study, we investigate the effect of SARS-CoV-2 infection on the frequency and phenotype of MAIT cells by flow cytometry, and we test in vitro stimulation conditions on the capacity to enhance or rescue the antiviral function of MAIT cells from patients with coronavirus disease 2019 (COVID-19). Our study, in agreement with recently published studies, confirmed the decline in MAIT cell frequency of hospitalized donors in comparison to healthy donors. MAIT cells of COVID-19 patients also had lower expression levels of TNF-alpha, perforin and granzyme B upon stimulation with IL-12 + IL-18. 24 h’ incubation with IL-7 successfully restored perforin expression levels in COVID-19 patients. Combined, our findings support the growing evidence that SARS-CoV-2 is dysregulating MAIT cells and that IL-7 treatment might improve their function, rendering them more effective in protecting the body against the virus.