A novel hemizygous CD40L mutation of X-linked hyper IgM syndromes and compound heterozygous DOCK8 mutations of hyper IgE syndromes in two Chinese families.

X-linked hyper-immunoglobulin M (X-HIGM) syndrome and autosomal recessive hyper-immunoglobulin E syndrome (HIES) are rare inborn errors of immunity characterized by recurrent infections due to immune system impairment. In this study, we identified a novel hemizygous CD40 ligand (CD40L) mutation and compound heterozygous dedicator of cytokinesis-8 (DOCK8) mutations in two Han Chinese families with X-HIGM and HIES, respectively. We aimed to investigate the association between their genotypes and phenotypes. Genomic DNA was extracted from peripheral blood samples obtained from the families. Whole exome sequencing and Sanger sequencing were performed to identify and verify pathogenic variants in the two families. Clinical analyses of the probands were also performed. A novel hemizygous mutation of CD40L in exon 2 (c.257delA) was identified in the first proband, resulting in the substitution of glycine with glutamic acid at codon 86 of the protein. This leads to premature termination of translation at downstream codon 9 (p.E86Gfs*9). Sanger sequencing confirmed that the variant was inherited from the mother. The second proband carried two novel compound heterozygous mutations in DOCK8: one at exon 14 (c.1546C > G) inherited from the father, and the other at intron 41 (c.5355 + 6C > T; splicing) inherited from the mother. This study enhances our understanding of the pathogenetic mutation spectrum of CD40L and DOCK8 genes, facilitating the prenatal diagnosis of X-HIGM and HIES and enabling timely treatment of patients.

Staphylococcus aureus Serine protease-like protein A (SplA) induces IL-8 by keratinocytes and synergizes with IL-17A.

BACKGROUND: Serine protease-like (Spl) proteins produced by Staphylococcus (S.) aureus have been associated with allergic inflammation. However, effects of Spls on the epidermal immune response have not been investigated. OBJECTIVES: To assess the epidermal immune response to SplA, SplD and SplE dependent on differentiation of keratinocytes and a Th2 or Th17 cytokine milieu. METHODS: Human keratinocytes of healthy controls and a STAT3-hyper-IgE syndrome (STAT3-HIES) patient were cultured in different calcium concentrations in the presence of Spls and Th2 or Th17 cytokines. Keratinocyte-specific IL-8 production and concomitant migration of neutrophils were assessed. RESULTS: SplE and more significantly SplA, induced IL-8 in keratinocytes. Suprabasal-like keratinocytes showed a higher Spl-mediated IL-8 production and neutrophil migration compared to basal-like keratinocytes. Th17 cytokines amplified Spl-mediated IL-8 production, which correlated with neutrophil recruitment. Neutrophil recruitment by keratinocytes of the STAT3-HIES patient was similar to healthy control cells. CONCLUSION: S. aureus-specific Spl proteases synergized with IL-17A on human keratinocytes with respect to IL-8 release and neutrophil migration, highlighting the importance of keratinocytes and Th17 immunity in barrier function.

Clinical, immunological, and genetic description of a Mexican cohort of patients with DOCK8 deficiency.

PURPOSE: We aimed to describe the clinical, immunological, and genetic features of patients with DOCK8 deficiency (DOCK8-Def) in a tertiary care center for children. METHODS: Retrospective chart review of patients' clinical, immunological, and genetic characteristics with DOCK8-Def. Genetic analysis was performed with targeted- or whole-exome sequencing; we also assessed DOCK8 protein expression and a lymphoproliferation assay and analyzed survival by the Kaplan-Meier method. RESULTS: We described 11 patients from 8 unrelated kindreds. The median age at symptoms' onset was 10 months (range 1-54 months). The median follow-up time was 53.4 months (4.8-118.8). All patients presented eczema and recurrent sinopulmonary and cutaneous infections. Besides those symptoms, the most frequent manifestations were bronchiectases (8/11), food allergies (6/11), and severe infections (6/11). Infrequent characteristics were detection of CMV in bronchial lavage, C. parvum-driven sclerosing cholangitis, Takayasu vasculitis, neurological syndromes, pulmonary tuberculosis, and lymphomatoid granulomatosis. CONCLUSION: DOCK8-Def has a broad spectrum of manifestations, including allergy, autoimmunity, inflammation, infection, and cancer. The hallmark of this inborn error of immunity is IEI-associated eczema with eosinophilia and increased IgE. Here, we report six new mutations causing human DOCK8 deficiency and symptoms previously unrecognized to occur in DOCK8-Def. Therefore, an early diagnosis of DOCK8-Def is essential to facilitate an adequate treatment such as HSCT.

Expanding the clinical and immunological phenotype of prolidase deficiency: A case report.

Prolidase deficiency (PD) is a rare autosomal recessive disorder associated with recurrent infections, immune dysregulation, and autoimmunity. PD is characterized by persistent dermatitis, skin fragility, and non-healing ulcerations on the lower limbs as its main dermatologic characteristics. Herein, we report a boy with PD due to a novel variant in PEPD who had abnormal facies, cognitive impairment, corneal opacity, recurrent infections, and persistent non-healing leg ulcers. Th17 lymphocyte counts and phosphorylated-STAT5 expression following IL-2 stimulation were reduced in our patient as compared to healthy control.

STAT6 gain-of-function variant exacerbates multiple allergic symptoms.

BACKGROUND: Allergic diseases were long considered to be complex multifactorial disorders. However, recent findings indicate that severe allergic inflammation can be caused by monogenic immune defects. OBJECTIVES: We sought to clarify the molecular pathogenesis of a patient with early-onset multiple allergic diseases, a high serum IgE level, hypereosinophilia, treatment-resistant severe atopic dermatitis with increased dermal collagen fiber deposition, and eosinophilic gastrointestinal disorder with numerous polypoid nodules. METHODS: A missense variant in STAT6 was identified, and its function was examined using peripheral blood, transfected HEK293 cells, lymphoblastoid cell lines, and knock-in mice with the corresponding mutation. RESULTS: Whole-exome sequencing identified a de novo heterozygous missense variant in signal transducer and activator of transcription 6 (STAT6) (p.Asp419Asn). Luciferase reporter assay revealed that the transcriptional activity of this STAT6 mutant was upregulated even without IL-4 stimulation. Phosphorylation of STAT6 was not observed in either the patient's TH2 cells or lymphoblastoid cell lines without stimulation, whereas it was induced more strongly in both by IL-4 stimulation compared with healthy controls. STAT6 protein was present in the nuclear fraction of the lymphoblastoid cell lines of the patient even in the absence of IL-4 stimulation. The patient's gastric mucosa showed upregulation of STAT6-, fibrosis-, and germinal center formation-related molecules. Some of the knock-in mice with the corresponding mutation spontaneously developed dermatitis with skin thickening and eosinophil infiltration. Moreover, serum IgE levels and mRNA expression of type 2 cytokines were increased in the knock-in mice-with or without development of spontaneous dermatitis-compared with the wild-type mice. CONCLUSIONS: A novel STAT6 gain-of-function variant is a potential cause of primary atopic disorders.

New Dominant-Negative IL6ST Variants Expand the Immunological and Clinical Spectrum of GP130-Dependent Hyper-IgE Syndrome.

Patients with autosomal dominant (AD) hyper-IgE syndrome (HIES) suffer from a constellation of manifestations including recurrent bacterial and fungal infections, severe atopy, and skeletal abnormalities. This condition is typically caused by monoallelic dominant-negative (DN) STAT3 variants. In 2020, we described 12 patients from eight kindreds with DN IL6ST variants resulting in a new form of AD HIES. These variants encoded truncated GP130 receptors, with intact extracellular and transmembrane domains, but lacking the intracellular recycling motif and the four STAT3-binding residues, resulting in an inability to recycle and activate STAT3. We report here two new DN variants of IL6ST in three unrelated families with HIES-AD. The biochemical and clinical impacts of these variants are different from those of the previously reported variants. The p.(Ser731Valfs*8) variant, identified in seven patients from two families, lacks the recycling motif and all the STAT3-binding residues, but its levels on the cell surface are only slightly increased and it underlies mild biological phenotypes with variable clinical expressivity. The p.(Arg768*) variant, identified in a single patient, lacks the recycling motif and the three most distal STAT3-binding residues. This variant accumulates at the cell surface and underlies severe biological and clinical phenotypes. The p.(Ser731Valfs*8) variant shows that a DN GP130 expressed at near normal levels on the cell surface can underlie heterogeneous clinical presentations, ranging from mild to severe. The p.(Arg768*) variant demonstrates that a truncated GP130 protein retaining one STAT3-binding residue can underlie severe HIES.

Idiopathic non-cirrhotic portal hypertension in a patient with Talaromyces marneffei infection: a case report.

BACKGROUND: The etiopathogenesis of idiopathic non-cirrhotic portal hypertension (INCPH) is so far poorly understood. Altered immunity, blood diseases, infections, congenital defects and drug exposure have been documented in a part of patients with INCPH owing to increased recognition of the disorder in patients with HIV, or various haematological disorders or autoimmune diseases. We aim to discuss the possible etiopathogenesis of INCPH. CASE PRESENTATION: We reported that a patient with intestinal infection of T. Marneffei and hyper-IgE syndrome, a group of rare primary immunodeficiency disorders, was finally diagnosed with INCPH for gastroesophageal variceal bleeding. The diagnosis was mainly based on histopathological features. Transjugular intrahepatic portosystemic shunt was performed and there was no recurrence of melena during the six-month follow-up. CONCLUSION: In the context of immunodeficiency, INCPH may associated with intestinal infections. Thus, screening for enterogenic infection and immunological disorders in patients with unexplained portal hypertension is necessary.

Interventional pulmonary procedures and their outcomes in patients with STAT3 hyper IgE syndrome.

BACKGROUND: STAT3 hyperimmunoglobulin E syndrome (STAT3-HIES) also referred to as autosomal dominant HIES (AD-HIES) is an inborn error of immunity characterized by the classic triad of eczema, frequent opportunistic infections, and elevated serum IgE levels. As a consequence of lung sequels due to repeated infections and impaired tissue healing, patients may require interventional pulmonary procedures. METHOD: Four patients with dominant-negative STAT3 mutations who had received interventional pulmonary procedures were enrolled. The demographic, clinical, and molecular characteristics were gathered through a medical record search. All reported STAT3-HIES patients in the literature requiring pulmonary procedures as part of their treatment were reviewed. RESULT: Recurrent episodes of pneumonia and lung abscess were the most prevalent symptoms. The most common non-immunological features were scoliosis, failure to thrive, and dental problems such as primary teeth retention and disseminated decays. Bronchiectasis, lung abscess, pneumatocele, and cavitary lesion were the most prevalent finding on high-resolution computed tomography at the earliest recording. All patients underwent pulmonary surgery and two of them experienced complications. CONCLUSION: Patients with STAT3-HIES have marked pulmonary infection susceptibility which may necessitate thoracic surgeries. Since surgical procedures involve a high risk of complication, surgical options are recommended to be utilized only in cases of drug resistance or emergencies.

STAT3-confusion-of-function: Beyond the loss and gain dualism.

BACKGROUND: Germline mutations of signal transducer and activator of transcription 3 (STAT3) are responsible for 2 distinct human diseases: autosomal-dominant hyper-IgE syndrome (AD-HIES) caused by STAT3 loss-of-function mutations and STAT3 gain-of-function disease. So far, these entities have been regarded as antithetic, with AD-HIES mainly associated with characteristic infections and a connective tissue phenotype and STAT3 gain-of-function characterized by lymphoproliferation and poly-autoimmunity. The R335W substitution in the DNA-binding domain of STAT3 was initially described in 2 patients with typical AD-HIES, but paradoxically, recent functional analysis demonstrated a gain-of-function effect of this variant. OBJECTIVES: A patient with Sjögren syndrome and features of AD-HIES with this mutation is described and the molecular consequences are further characterized. METHODS: This study provides a clinical and immunological description of the patient. STAT phosphorylation in primary patient cells was studied and A4 cells transfected with the patient allele were used to study phosphorylation kinetics, transcriptional activity, and target-gene induction. RESULTS: The hybrid clinical features of the patient were associated with normal TH17 cells. Enhanced and prolonged STAT3 phosphorylation, an increased STAT3 driven luciferase reporter activity upon IL-6 stimulation, but reduced IL-6-induced SOCS3 production were all observed. CONCLUSIONS: The germline R335W-STAT3 variant displays a mixed behavior in vitro that mainly shows gain-of-function, but also loss-of-function features. This is matched by an ambiguous clinical and immunological phenotype that dismantles the classical antithetic dualism of gain- versus loss-of-function. Germline STAT3 mutation-related disease represents a pathological spectrum with the p.R335W associated phenotype locating between the 2 recognized clinical disease patterns.

Multi-Omics Profiling in PGM3 and STAT3 Deficiencies: A Tale of Two Patients.

Hyper-IgE Syndrome (HIES) is a heterogeneous group of primary immune-deficiency disorders characterized by elevated levels of IgE, eczema, and recurrent skin and lung infections. HIES that is autosomally dominant in the signal transducer and activator of transcription 3 (STAT3), and autosomal recessive mutations in phosphoglucomutase 3 (PGM3) have been reported in humans. An early diagnosis, based on clinical suspicion and immunological assessments, is challenging. Patients' metabolomics, proteomics, and cytokine profiles were compared to DOCK 8-deficient and atopic dermatitis patients. The PGM3 metabolomics profile identified significant dysregulation in hypotaurine, hypoxanthine, uridine, and ribothymidine. The eight proteins involved include bifunctional arginine demethylase and lysyl hydroxylase (JMJD1B), type 1 protein phosphatase inhibitor 4 (PPI 4), and platelet factor 4 which aligned with an increased level of the cytokine GCSF. Patients with STAT3 deficiency, on the other hand, showed significant dysregulation in eight metabolites, including an increase in protocatechuic acid, seven proteins including ceruloplasmin, and a plasma protease C1 inhibitor, in addition to cytokine VEGF being dysregulated. Using multi-omics profiling, we identified the dysregulation of endothelial growth factor (EGFR) and tumor necrosis factor (TNF) signaling pathways in PGM3 and STAT3 patients, respectively. Our findings may serve as a stepping stone for larger prospective HIES clinical cohorts to validate their future use as biomarkers.

Dupilumab in the treatment of genodermatosis: A systematic review.

Dupilumab interferes with the signaling pathways of IL-4 and IL-13 and is effective in treating atopic dermatitis. Specific genodermatoses, including Netherton syndrome, epidermolysis bullosa pruriginosa, and hyper-IgE syndrome, are Th2 skewed diseases with activation of type 2 inflammation. We performed this systematic review to investigate the therapeutic role of dupilumab in the treatment of genodermatosis. A systematic search was conducted of the PubMed, Embase, Web of Science, and Cochrane databases from inception to December 13, 2021. The review included studies with relevant terms including "dupilumab," "genodermatosis", "Netherton syndrome", "ichthyosis", "epidermolysis bullosa" and "hyper-IgE syndrome". The initial search yielded 2,888 results, of which 28 studies and 37 patients with genodermatosis were enrolled. The assessed genodermatoses included Netherton syndrome, epidermolysis bullosa pruriginosa, hyper-IgE syndrome, Hailey-Hailey disease, and severe eczema associated with genetic disorders. Most of the reported cases showed significant clinical improvement after the initiation of dupilumab treatment without major adverse events. Decreased immunoglobulin E levels and cytokine normalization have also been documented. In conclusion, Dupilumab may have a potential therapeutic role in certain genodermatoses skewed towards T helper 2 (Th2) immunity, including Netherton syndrome, epidermolysis bullosa pruriginosa, hyper-IgE syndrome, Hailey-Hailey disease, and severe eczema associated with some genetic disorders.

Intraoral and maxillofacial abnormalities in patients with autosomal dominant hyper-IgE syndrome.

Autosomal dominant hyper-IgE syndrome (AD-HIES) is an inborn error of immunity (IEI) caused by a dominant-negative mutation in the signal transducer and activator of transcription 3 (STAT 3). This disease is characterized by chronic eczematoid dermatitis, recurrent staphylococcal skin abscesses, pneumonia, pneumatoceles, and extremely high serum IgE levels. Loss-of-function STAT3 mutations may also result in distinct non-immunologic features such as dental, facial, skeletal, and vascular abnormalities, central nervous system malformations and an increased risk for bone fractures. Prophylactic treatment of Candida infections and prophylactic antimicrobial therapy for staphylococcal skin infections and sinopulmonary infections are essential. An awareness of the oral and maxillofacial features of HIES may facilitate early diagnosis with genetic counselling and may improve future patient care. This study describes oral, dental, and maxillofacial manifestations in 14 patients with genetically defined AD-HIES. We also review the literature and propose recommendations for the complex care of patients with this rare primary immunodeficiency.

Hyper IgE syndromes: A clinical approach.

Hyper IgE syndromes (HIESs) are a group of rare inborn errors of immunity with a triad of eczema, increase susceptibility to sinopulmonary and skin infections with high level of IgE serum. Although most of HIESs are sporadic, hereditary types of these disorders have been studied well. There are several distinct immunodeficiency disorders which are phenotypically similar to HIES, and thus make the diagnosis of HIES challenging. In fact, the diagnosis of HIES is typically based on the clinical suspicion and immunological assessments. There is yet no specific curative treatment for most of HIESs at present, and the treatments are mostly standing on early diagnosis and preventive therapies. For instance, the genetic diagnosis is an important module, while, due to DOCK8 mutations, the hematopoietic stem cell transplantation is necessary for patients with autosomal recessive form of HIESs. Herein, we overview HIESs, highlight their peculiar clinical and laboratory features, and finally suggest a practical forthright diagnostic chart for clinical purposes.

Molecular Assessment of Staphylococcus Aureus Strains in STAT3 Hyper-IgE Syndrome Patients.

Hyper-IgE syndromes (HIES) are a group of inborn errors of immunity (IEI) caused by monogenic defects such as in the gene STAT3 (STAT3-HIES). Patients suffering from HIES show an increased susceptibility to Staphylococcus aureus (S. aureus) including skin abscesses and pulmonary infections. To assess if the underlying immune defect of STAT3-HIES patients influences the resistance patterns, pathogenicity factors or strain types of S. aureus. We characterized eleven S. aureus strains isolated from STAT3-HIES patients (n = 4) by whole genome sequencing (WGS) to determine presence of resistance and virulence genes. Additionally, we used multi-locus sequence typing (MLST) and protein A (spa) typing to classify these isolates. Bacterial isolates collected from this cohort of STAT3-HIES patients were identified as common spa types in Germany. Only one of the isolates was classified as methicillin-resistant S. aureus (MRSA). For one STAT3 patient WGS illustrated that infection and colonization occurred with different S. aureus isolates rather than one particular clone. The identified S. aureus carriage profile on a molecular level suggests that S. aureus strain type in STAT3-HIES patients is determined by local epidemiology rather than the underlying immune defect highlighting the importance of microbiological assessment prior to antibiotic treatment.

Profound differences in IgE and IgG recognition of micro-arrayed allergens in hyper-IgE syndromes.

BACKGROUND: The specificities of IgE and IgG for allergen molecules in patients with inborn errors of immunity (IEI) have not been investigated in detail. OBJECTIVE: To study IgE and IgG antibody specificities in patients with defined hyper-IgE syndromes (HIES) using a comprehensive panel of allergen molecules. METHODS: We used chips containing micro-arrayed allergen molecules to analyze allergen-specific IgE and IgG levels in sera from two groups of HIES patients: Autosomal recessive mutations in phosphoglucomutase-3 (PGM3); Autosomal dominant negative mutations of STAT3 (STAT3); and age-matched subjects with allergic sensitizations. Assays with rat basophil leukemia cells transfected with human FcεRI were performed to study the biological relevance of IgE sensitizations. RESULTS: Median total IgE levels were significantly lower in the sensitized control group (212.9 kU/L) as compared to PGM3 (5042 kU/L) and STAT3 patients (2561 kU/L). However, PGM3 patients had significantly higher allergen-specific IgE levels and were sensitized to a larger number of allergen molecules as compared to STAT3 patients. Biological relevance of IgE sensitization was confirmed for PGM3 patients by basophil activation testing. PGM3 patients showed significantly lower cumulative allergen-specific IgG responses in particular to milk and egg allergens as compared to STAT3 patients and sensitized controls whereas total IgG levels were comparable to STAT3 patients and significantly higher than in controls. CONCLUSION: The analysis with multiple micro-arrayed allergen molecules reveals profound differences of allergen-specific IgE and IgG recognition in PGM3 and STAT3 patients which may be useful for classification of IEI and clinical characterization of patients.

IgE Sensitization Profile in Patients with Netherton Syndrome.

BACKGROUND: Scant data are currently available on the allergen-specific immunoglobulin (Ig)E sensitization profile in primary immunodeficiencies with hyper IgE. Netherton syndrome (NS, OMIM 266500) is an extremely rare form of congenital ichthyosis characterized by congenital scaly erythroderma, hair abnormalities, and deregulated IgE reactivity associated with severe atopic manifestations. OBJECTIVE: The aim of this study was to evaluate the feasibility and reliability of a multiplex proteomic approach in the detection of specific IgE in NS. METHODS: Specific IgE was evaluated in 10 individuals with an established molecular diagnosis of NS using an allergenic molecules microarray (immuno-solid-phase allergen chip). RESULTS: Polireactivity to airway allergens, mainly house dust mites and olive tree pollen, and food allergens were observed in NS. Eighty per cent of patients were responsive to LTP or profilins. A clinical history suggestive of severe egg, milk, and fish allergy was confirmed by reactivity to the thermostable molecules Gal d 1, Bod 8, and parvalbumin Gad c 1, respectively. Latex reactivity was associated with Hev b 5 and 6 reactivity. Two distinct clusters of reactivity were observed after hierarchical analysis. Extremely high IgE levels (> 10,000 kU/L) do not affect the results obtained with microarrays. CONCLUSION: IgE multiplex evaluation allows (i) to profile IgE polyreactivity pictures, in the presence of LTP and profilin sensitization, (ii) to verify the clinical history of food allergy to milk, egg, and seafood, (iii) to confirm the allergic events associated with latex exposure, and (iv) to disclose the presence of preclinical sensitizations in patients affected by primary immunodeficiencies with hyper IgE, such as the NS.

Novel mutations of TYK2 leading to divergent clinical phenotypes.

BACKGROUND: TYK2 deficiency is a rare primary immunodeficiency disease caused by loss-of-function mutations of TYK2 gene, which is initially proposed as a subset of hyper-IgE syndrome (HIES). However, accumulating evidence suggests TYK2-deficient patients do not necessarily present with HIES characteristics, indicating a vacuum of knowledge on the exact roles of TYK2 in human immune system. METHOD: Pathogenic effects of patients were confirmed by qRT-PCR, Western blot, and protein stability assays. The responses to cytokines including IFN-α/ß/γ, IL-6, IL-10, IL-12, and IL-23 of peripheral blood mononuclear cells (PBMCs) from these patients were detected by Western blot, qRT-PCR, and flow cytometry. The differentiation of T and B cells was detected by flow cytometry. RESULTS: We described five more TYK2-deficient cases presenting with or without hyper-IgE levels, atopy, and distinct pathogen infection profile, which are caused by novel TYK2 mutations. These mutations were all found by high-throughput sequencing and confirmed by Sanger sequencing. The patients showed heterogeneous responses to various cytokine treatments, including IFN-α/ß/γ, IL-6, IL-10, IL-12, and IL-23. The homeostasis of lymphocytes is also disrupted. CONCLUSION: Based on our findings, we propose that TYK2 works as a multi-tasker in orchestrating various cytokine signaling pathways, differentially combined defects which account for the expressed clinical manifestations.

Clearance of atypical cutaneous manifestations of hyper-IgE syndrome with dupilumab.

Hyper-IgE syndromes (HIES) are a heterogeneous group of rare primary immunodeficiency diseases classically characterized by the triad of atopic dermatitis, and recurrent cutaneous and pulmonary infections. Autosomal dominant, loss-of-function STAT3 pathogenic variants are the most common genetic cause, which lead to deficiency of Th17 lymphocytes, impaired interferon gamma production, and IL-10 signal transduction, and an unbalanced IL-4 state. Dupilumab, a monoclonal antibody to the IL-4a receptor, inhibits both IL-4 and IL-13, and has been shown to improve atopic dermatitis and other manifestations of HIES including asthma and allergic bronchopulmonary aspergillosis. We present a pediatric patient with HIES who presented predominantly with eosinophilic folliculitis, recurrent cutaneous infections, and other non-eczematous findings and achieved sustained clearance with dupilumab.

A deep intronic splice mutation of STAT3 underlies hyper IgE syndrome by negative dominance.

Heterozygous in-frame mutations in coding regions of human STAT3 underlie the only known autosomal dominant form of hyper IgE syndrome (AD HIES). About 5% of familial cases remain unexplained. The mutant proteins are loss-of-function and dominant-negative when tested following overproduction in recipient cells. However, the production of mutant proteins has not been detected and quantified in the cells of heterozygous patients. We report a deep intronic heterozygous STAT3 mutation, c.1282-89C>T, in 7 relatives with AD HIES. This mutation creates a new exon in the STAT3 complementary DNA, which, when overexpressed, generates a mutant STAT3 protein (D427ins17) that is loss-of-function and dominant-negative in terms of tyrosine phosphorylation, DNA binding, and transcriptional activity. In immortalized B cells from these patients, the D427ins17 protein was 2 kDa larger and 4-fold less abundant than wild-type STAT3, on mass spectrometry. The patients' primary B and T lymphocytes responded poorly to STAT3-dependent cytokines. These findings are reminiscent of the impaired responses of leukocytes from other patients with AD HIES due to typical STAT3 coding mutations, providing further evidence for the dominance of the mutant intronic allele. These findings highlight the importance of sequencing STAT3 introns in patients with HIES without candidate variants in coding regions and essential splice sites. They also show that AD HIES-causing STAT3 mutant alleles can be dominant-negative even if the encoded protein is produced in significantly smaller amounts than wild-type STAT3.

Functional and structural analysis of cytokine-selective IL6ST defects that cause recessive hyper-IgE syndrome.

BACKGROUND: Biallelic variants in IL6ST, encoding GP130, cause a recessive form of hyper-IgE syndrome (HIES) characterized by high IgE level, eosinophilia, defective acute phase response, susceptibility to bacterial infections, and skeletal abnormalities due to cytokine-selective loss of function in GP130, with defective IL-6 and IL-11 and variable oncostatin M (OSM) and IL-27 levels but sparing leukemia inhibitory factor (LIF) signaling. OBJECTIVE: Our aim was to understand the functional and structural impact of recessive HIES-associated IL6ST variants. METHODS: We investigated a patient with HIES by using exome, genome, and RNA sequencing. Functional assays assessed IL-6, IL-11, IL-27, OSM, LIF, CT-1, CLC, and CNTF signaling. Molecular dynamics simulations and structural modeling of GP130 cytokine receptor complexes were performed. RESULTS: We identified a patient with compound heterozygous novel missense variants in IL6ST (p.Ala517Pro and the exon-skipping null variant p.Gly484_Pro518delinsArg). The p.Ala517Pro variant resulted in a more profound IL-6- and IL-11-dominated signaling defect than did the previously identified recessive HIES IL6ST variants p.Asn404Tyr and p.Pro498Leu. Molecular dynamics simulations suggested that the p.Ala517Pro and p.Asn404Tyr variants result in increased flexibility of the extracellular membrane-proximal domains of GP130. We propose a structural model that explains the cytokine selectivity of pathogenic IL6ST variants that result in recessive HIES. The variants destabilized the conformation of the hexameric cytokine receptor complexes, whereas the trimeric LIF-GP130-LIFR complex remained stable through an additional membrane-proximal interaction. Deletion of this membrane-proximal interaction site in GP130 consequently caused additional defective LIF signaling and Stüve-Wiedemann syndrome. CONCLUSION: Our data provide a structural basis to understand clinical phenotypes in patients with IL6ST variants.