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Pathogenic variants in the transcription factor TP63 are associated with clinically overlapping syndromes including ectrodactyly-ectodermal dysplasia clefting (EEC) and ankyloblepharon-ectodermal defects-cleft lip/palate (AEC). T cell lymphopenia has rarely been described in individuals with TP63 variants and the cause of the T cell defect is unclear. Here, we present a case of a female infant born with TP63 -related syndrome and profound T cell lymphopenia, first uncovered through newborn screening. Flow cytometry analysis revealed low CD4+ naïve T cells and nearly absent CD8+ T cells with intact B and NK cell compartments. A de novo heterozygous pathogenic variant c.1040 G>A (C347Y) in exon 8 of TP63 was identified. An artificial thymic organoid system, to assess the intrinsic ability of the patient's hematopoietic cells to develop into T cells, was performed twice using separate peripheral blood samples. Ex vivo T cell differentiation was evident with the artificial organoid system, suggesting that a thymic stromal cell defect may be the cause of the T cell lymphopenia. Consistent with this, interrogation of publicly available data indicated that TP63 expression in the human thymus is restricted to thymic epithelial cells. Based on these data, congenital athymia was suspected and the patient received an allogenic cultured thymus tissue implant (CTTI). This is the first report of suspected congenital athymia and attempted treatment with CTTI associated with TP63 variant. At 9 months post-implant, peripheral lymphocyte analysis revealed measurable T cell receptor excision circles and presence of CD4+ recent thymic emigrants suggestive of early thymopoiesis. She will continue regular monitoring to ensure restoration of T cell immunity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Gall, Bosticardo, Ma, Chen, Amini, Pala, Delmonte, Wenger, Bamshad, Sleasman, Blessing, van Oers, Notarangelo and de la Morena.)

Background: Thymus hypoplasia due to stromal cell problems has been linked to mutations in several transcription factors, including Forkhead box N1 (FOXN1). FOXN1 supports T-cell development by regulating the formation and expansion of thymic epithelial cells (TECs). While autosomal recessive FOXN1 mutations result in a nude and severe combined immunodeficiency phenotype, the impact of single-allelic or compound heterozygous FOXN1 mutations is less well-defined., Objective: With more than 400 FOXN1 mutations reported, their impact on protein function and thymopoiesis remains unclear for most variants. We developed a systematic approach to delineate the functional impact of diverse FOXN1 variants., Methods: Selected FOXN1 variants were tested with transcriptional reporter assays and imaging studies. Thymopoiesis was assessed in mouse lines genocopying several human FOXN1 variants. Reaggregate thymus organ cultures were used to compare the thymopoietic potential of the FOXN1 variants., Results: FOXN1 variants were categorized into benign, loss- or gain-of-function, and/or dominant-negatives. Dominant negative activities mapped to frameshift variants impacting the transactivation domain. A nuclear localization signal was mapped within the DNA binding domain. Thymopoiesis analyses with mouse models and reaggregate thymus organ cultures revealed distinct consequences of particular Foxn1 variants on T-cell development., Conclusions: The potential effect of a FOXN1 variant on T-cell output from the thymus may relate to its effects on transcriptional activity, nuclear localization, and/or dominant negative functions. A combination of functional assays and thymopoiesis comparisons enabled a categorization of diverse FOXN1 variants and their potential impact on T-cell output from the thymus., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: To understand the natural history and clinical outcomes for patients with X-linked agammaglobulinemia (XLA) in the United States utilizing the United States Immunodeficiency Network (USIDNET) patient registry., Methods: The USIDNET registry was queried for data from XLA patients collected from 1981 to 2019. Data fields included demographics, clinical features before and after diagnosis of XLA, family history, genetic mutation in Bruton's tyrosine kinase (BTK), laboratory findings, treatment modalities, and mortality., Results: Data compiled through the USIDNET registry on 240 patients were analyzed. Patient year of birth ranged from 1945 to 2017. Living status was available for 178 patients; 158/178 (88.8%) were alive. Race was reported for 204 patients as follows: White, 148 (72.5%); Black/African American, 23 (11.2%); Hispanic, 20 (9.8%); Asian or Pacific Islander, 6 (2.9%), and other or more than one race, 7 (3.4%). The median age at last entry, age at disease onset, age at diagnosis, and length of time with XLA diagnosis was 15 [range (r) = 1-52 years], 0.8 [r = birth-22.3 years], 2 [r = birth-29 years], and 10 [r = 1-56 years] years respectively. One hundred and forty-one patients (58.7%) were < 18 years of age. Two hundred and twenty-one (92%) patients were receiving IgG replacement (IgGR), 58 (24%) were on prophylactic antibiotics, and 19 (7.9%) were on immunomodulatory drugs. Eighty-six (35.9%) patients had undergone surgical procedures, two had undergone hematopoietic cell transplantation, and two required liver transplantation. The respiratory tract was the most affected organ system (51.2% of patients) followed by gastrointestinal (40%), neurological (35.4%), and musculoskeletal (28.3%). Infections were common both before and after diagnosis, despite IgGR therapy. Bacteremia/sepsis and meningitis were reported more frequently before XLA diagnosis while encephalitis was more commonly reported after diagnosis. Twenty patients had died (11.2%). The median age of death was 21 years (range = 3-56.7 years). Neurologic condition was the most common underlying co-morbidity for those XLA patients who died., Conclusions: Current therapies for XLA patients reduce early mortality, but patients continue to experience complications that impact organ function. With improved life expectancy, more efforts will be required to improve post-diagnosis organ dysfunction and quality of life. Neurologic manifestations are an important co-morbidity associated with mortality and not yet clearly fully understood., (© 2023. The Author(s).)

Current practices vary widely regarding the immunological work-up and management of patients affected with defects in thymic development (DTD), which include chromosome 22q11.2 microdeletion syndrome (22q11.2del) and other causes of DiGeorge syndrome (DGS) and coloboma, heart defect, atresia choanae, retardation of growth and development, genital hypoplasia, ear anomalies/deafness (CHARGE) syndrome. Practice variations affect the initial and subsequent assessment of immune function, the terminology used to describe the condition and immune status, the accepted criteria for recommending live vaccines, and how often follow-up is needed based on the degree of immune compromise. The lack of consensus and widely varying practices highlight the need to establish updated immunological clinical practice guidelines. These guideline recommendations provide a comprehensive review for immunologists and other clinicians who manage immune aspects of this group of disorders., (© 2023. The Author(s).)

22q11.2 deletion syndrome (22q11.2DS) is the most common human chromosomal microdeletion, causing developmentally linked congenital malformations, thymic hypoplasia, hypoparathyroidism, and/or cardiac defects. Thymic hypoplasia leads to T cell lymphopenia, which most often results in mild SCID. Despite decades of research, the molecular underpinnings leading to thymic hypoplasia in 22q11.2DS remain unknown. Comparison of embryonic thymuses from mouse models of 22q11.2DS (Tbx1neo2/neo2) revealed proportions of mesenchymal, epithelial, and hematopoietic cell types similar to those of control thymuses. Yet, the small thymuses were growth restricted in fetal organ cultures. Replacement of Tbx1neo2/neo2 thymic mesenchymal cells with normal ones restored tissue growth. Comparative single-cell RNA-Seq of embryonic thymuses uncovered 17 distinct cell subsets, with transcriptome differences predominant in the 5 mesenchymal subsets from the Tbx1neo2/neo2 cell line. The transcripts affected included those for extracellular matrix proteins, consistent with the increased collagen deposition we observed in the small thymuses. Attenuating collagen cross-links with minoxidil restored thymic tissue expansion for hypoplastic lobes. In colony-forming assays, the Tbx1neo2/neo2-derived mesenchymal cells had reduced expansion potential, in contrast to the normal growth of thymic epithelial cells. These findings suggest that mesenchymal cells were causal to the small embryonic thymuses in the 22q11.2DS mouse models, which was correctable by substitution with normal mesenchyme.

Type I interferons (IFN-I) play a critical role in human antiviral immunity, as demonstrated by the exceptionally rare deleterious variants of IFNAR1 or IFNAR2. We investigated five children from Greenland, Canada, and Alaska presenting with viral diseases, including life-threatening COVID-19 or influenza, in addition to meningoencephalitis and/or hemophagocytic lymphohistiocytosis following live-attenuated viral vaccination. The affected individuals bore the same homozygous IFNAR2 c.157T>C, p.Ser53Pro missense variant. Although absent from reference databases, p.Ser53Pro occurred with a minor allele frequency of 0.034 in their Inuit ancestry. The serine to proline substitution prevented cell surface expression of IFNAR2 protein, small amounts of which persisted intracellularly in an aberrantly glycosylated state. Cells exclusively expressing the p.Ser53Pro variant lacked responses to recombinant IFN-I and displayed heightened vulnerability to multiple viruses in vitro-a phenotype rescued by wild-type IFNAR2 complementation. This novel form of autosomal recessive IFNAR2 deficiency reinforces the essential role of IFN-I in viral immunity. Further studies are warranted to assess the need for population screening., (© 2022 Duncan et al.)

The SKIV2L RNA exosome is an evolutionarily conserved RNA degradation complex in the eukaryotes. Mutations in the SKIV2L gene are associated with a severe inherited disorder, trichohepatoenteric syndrome (THES), with multisystem involvement but unknown disease mechanism. Here, we reported a THES patient with SKIV2L mutations showing severe primary B cell immunodeficiency, hypogammaglobulinemia, and kappa-restricted plasma cell dyscrasia but normal T cell and NK cell function. To corroborate these findings, we made B cell-specific Skiv2l knockout mice ( Skiv2l fl/fl Cd79a-Cre ), which lacked both conventional B-2 and innate-like B-1 B cells in the periphery and secondary lymphoid organs. This was linked to a requirement of SKIV2L RNA exosome activity in the bone marrow during early B cell development at the pro-B cell to large pre-B cell transition. Mechanistically, Skiv2l -deficient pro-B cells exhibited cell cycle arrest and DNA damage. Furthermore, loss of Skiv2l led to substantial out-of-frame V(D)J rearrangement of immunoglobulin heavy chain and severely reduced surface expression of μH, both of which are crucial for pre-BCR signaling and proliferative burst during early B cell development. Together, our data demonstrated a crucial role for SKIV2L RNA exosome in early B cell development in both human and mice by ensuring proper V(D)J recombination and Igh expression, which serves as the molecular basis for immunodeficiency associated with THES.

Purpose: X-linked agammaglobulinemia (XLA) is a primary immunodeficiency (PID) caused by a defect in the gene encoding for Bruton tyrosine kinase (BTK). In the absence of a functional BTK, patients have low or absent circulating B cells and low or absent serum immunoglobulin. Despite gammaglobulin replacement and prompt use of antimicrobial agents, patients with XLA continue to experience infectious and non-infectious complications throughout their lifetime. The purpose of this study was to understand self-perceived health status of US-based patients with XLA, and examine the associations amongst clinical characteristics, treatment experience, and quality of life (QoL)., Methods: A 46 and 68 question survey, developed by the Immune Deficiency Foundation (IDF) and a Short Form-12item v2® (SF-12v2®) for adults and SF-10™ for children to assess QoL, were mailed by IDF to patients in 2017 and 2018. Those that self-identified as having XLA or males with agammaglobulinemia were selected for analysis. Mean physical and mental composite scores (PCS and MCS) from SF-12v2® and mean physical health component (PHS) and psychological health summary (PSS) from SF-10™ scores were compared to the US normative data., Results: Ninety-one patients completed the surveys: 58 (63.7%) adults and 33 (36.3%) children. For the combined surveys, the overall median age at time of the survey was 28.5 years (yrs); Inter-Quartile-Range (IQR) 13-49.5 yrs; the median age at diagnosis was 2 yrs (IQR = 0-4 yrs) and the median number of years with XLA diagnosis was 23 (IQR 10.75-40yrs). Amongst adult patients, physical scores were noted to be below the general adult population but did not reach statistical significance. In contrast, 2 or more chronic conditions impacted both physical and mental QoL (p < .001) and hospitalization was associated with significantly decreased physical health QoL (p < .001); three or more infections in the past 12 months exhibited impact on physical health although was not found to be statistically significant. Adult patients with public insurance fared worse in mental health domains compared to those with combined public and private or those with private alone (p = 0.001). Employment status did not impact QoL. None of these variables met statistical significance nor demonstrated impact within the pediatric population in either physical or mental domains of health., Conclusion: Our study provides further insight into what factors impact both physical and mental domains of health amongst patients with XLA. Early detection to prevent the development of associated morbidity, as well as vigilant care to prevent hospitalizations and infections, can limit the impact this disease may have on the overall well-being of XLA patients., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Inborn errors of nucleic acid metabolism often cause aberrant activation of nucleic acid sensing pathways, leading to autoimmune or autoinflammatory diseases. The SKIV2L RNA exosome is cytoplasmic RNA degradation machinery that was thought to be essential for preventing the self-RNA-mediated interferon (IFN) response. Here, we demonstrate the physiological function of SKIV2L in mammals. We found that Skiv2l deficiency in mice disrupted epidermal and T cell homeostasis in a cell-intrinsic manner independently of IFN. Skiv2l-deficient mice developed skin inflammation and hair abnormality, which were also observed in a SKIV2L-deficient patient. Epidermis-specific deletion of Skiv2l caused hyperproliferation of keratinocytes and disrupted epidermal stratification, leading to impaired skin barrier with no appreciable IFN activation. Moreover, Skiv2l-deficient T cells were chronically hyperactivated and these T cells attacked lesional skin as well as hair follicles. Mechanistically, SKIV2L loss activated the mTORC1 pathway in both keratinocytes and T cells. Both systemic and topical rapamycin treatment of Skiv2l-deficient mice ameliorated epidermal hyperplasia and skin inflammation. Together, we demonstrate that mTORC1, a classical nutrient sensor, also senses cytoplasmic RNA quality control failure and drives autoinflammatory disease. We also propose SKIV2L-associated trichohepatoenteric syndrome (THES) as a new mTORopathy for which sirolimus may be a promising therapy.

Purpose: The human antibody repertoire forms in response to infections, the microbiome, vaccinations, and environmental exposures. The specificity of such antibody responses was compared among a cohort of toddlers to identify differences between seropositive versus seronegative responses., Methods: An assessment of the serum IgM and IgG antibody reactivities in 197 toddlers of 1- and 2-years of age was performed with a microfluidic array containing 110 distinct antigens. Longitudinal profiling was done from years 1 to 2. Seropositivity to RNA and DNA viruses; bacteria; live attenuated, inactive, and subunit vaccines; and autoantigens was compared. A stratification was developed based on quantitative variations in the IgG responses. Clinical presentations and previously known genetic risk alleles for various immune system conditions were investigated in relation to IgG responses., Results: IgG reactivities stratified toddlers into low, moderate, and high responder groups. The high group (17%) had elevated IgG responses to multiple RNA and DNA viruses (e.g., respiratory syncytial virus, Epstein-Barr virus, adenovirus, Coxsackievirus) and this correlated with increased responses to live attenuated viral vaccines and certain autoantigens. This high group was more likely to be associated with gestational diabetes and an older age. Genetic analyses identified polymorphisms in the IL2RB, TNFSF4, and INS genes in two high responder individuals that were associated with their elevated cytokine levels and clinical history of eczema and asthma., Conclusion: Serum IgG profiling of toddlers reveals correlations between the magnitude of the antibody responses towards viruses, live attenuated vaccines, and certain autoantigens. A low responder group had much weaker responses overall, including against vaccines. The serum antibody screen also identifies individuals with IgG responses to less common infections (West Nile virus, parvovirus, tuberculosis). The characterization of the antibody responses in combination with the identification of genetic risk alleles provides an opportunity to identify children with increased risk of clinical disease.

Very Early Onset Inflammatory Bowel Disease (VEO-IBD) represents a cohort of inflammatory bowel disease (IBD) patients diagnosed before 6 years of age. Unlike IBD diagnosed at older ages, VEO-IBD can be associated with underlying primary immunodeficiencies. VEO-IBD has been linked to monogenic variations in over 70 genes involved in multiple pathways of immunity. As sequencing technologies and platforms evolve and become readily available, an increasing number of genes linked to VEO-IBD have emerged. Although monogenic defects are rare in VEO-IBD, diagnosis of these variants can often dictate specific treatment. In this mini-review, we set out to describe monogenic variants previously characterized in multiple patients in the literature that contribute to VEO-IBD, diagnostic tools, unique treatment modalities for specific genetic diagnoses, and future directions in the field of VEO-IBD. Although this mini-review is by no means comprehensive of all the novel monogenic variants linked to VEO-IBD, we hope to provide relevant information that is readily accessible to clinicians and educators., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zheng, de la Morena and Suskind.)

Primary Immune Regulatory Disorders (PIRD) are an expanding group of diseases caused by gene defects in several different immune pathways, such as regulatory T cell function. Patients with PIRD develop clinical manifestations associated with diminished and exaggerated immune responses. Management of these patients is complicated; oftentimes immunosuppressive therapies are insufficient, and patients may require hematopoietic cell transplant (HCT) for treatment. Analysis of HCT data in PIRD patients have previously focused on a single gene defect. This study surveyed transplanted patients with a phenotypic clinical picture consistent with PIRD treated in 33 Primary Immune Deficiency Treatment Consortium centers and European centers. Our data showed that PIRD patients often had immunodeficient and autoimmune features affecting multiple organ systems. Transplantation resulted in resolution of disease manifestations in more than half of the patients with an overall 5-years survival of 67%. This study, the first to encompass disorders across the PIRD spectrum, highlights the need for further research in PIRD management., (Copyright © 2020 Chan, Leiding, Liu, Logan, Burroughs, Allenspach, Skoda-Smith, Uzel, Notarangelo, Slatter, Gennery, Smith, Pai, Jordan, Marsh, Cowan, Dvorak, Craddock, Prockop, Chandrakasan, Kapoor, Buckley, Parikh, Chellapandian, Oshrine, Bednarski, Cooper, Shenoy, Davila Saldana, Forbes, Martinez, Haddad, Shyr, Chen, Sullivan, Heimall, Wright, Bhatia, Cuvelier, Goldman, Meyts, Miller, Seidel, Vander Lugt, Bacchetta, Weinacht, Andolina, Caywood, Chong, de la Morena, Aquino, Shereck, Walter, Dorsey, Seroogy, Griffith, Kohn, Puck, Pulsipher and Torgerson.)

Chromosome 22q11.2 deletion syndrome (22q11.2del) is a complex, multi-organ disorder noted for its varying severity and penetrance among those affected. The clinical problems comprise congenital malformations; cardiac problems including outflow tract defects, hypoplasia of the thymus, hypoparathyroidism, and/or dysmorphic facial features. Additional clinical issues that can appear over time are autoimmunity, renal insufficiency, developmental delay, malignancy and neurological manifestations such as schizophrenia. The majority of individuals with 22q11.2del have a 3 Mb deletion of DNA on chromosome 22, leading to a haploinsufficiency of ~106 genes, which comprise coding RNAs, noncoding RNAs, and pseudogenes. The consequent haploinsufficiency of many of the coding genes are well described, including the key roles of T-box Transcription Factor 1 ( TBX1 ) and DiGeorge Critical Region 8 ( DGCR8 ) in the clinical phenotypes. However, the haploinsufficiency of these genes alone cannot account for the tremendous variation in the severity and penetrance of the clinical complications among those affected. Recent RNA and DNA sequencing approaches are uncovering novel genetic and epigenetic differences among 22q11.2del patients that can influence disease severity. In this review, the role of coding and non-coding genes, including microRNAs (miRNA) and long noncoding RNAs (lncRNAs), will be discussed in relation to their bearing on 22q11.2del with an emphasis on TBX1 ., (Copyright © 2020 Du, de la Morena and van Oers.)

We report on 2 patients with compound heterozygous mutations in forkhead box N1 (FOXN1), a transcription factor essential for thymic epithelial cell (TEC) differentiation. TECs are critical for T cell development. Both patients had a presentation consistent with T-/loB+NK+ SCID, with normal hair and nails, distinct from the classic nude/SCID phenotype in individuals with autosomal-recessive FOXN1 mutations. To understand the basis of this phenotype and the effects of the mutations on FOXN1, we generated mice using CRISPR-Cas9 technology to genocopy mutations in 1 of the patients. The mice with the Foxn1 compound heterozygous mutations had thymic hypoplasia, causing a T-B+NK+ SCID phenotype, whereas the hair and nails of these mice were normal. Characterization of the functional changes due to the Foxn1 mutations revealed a 5-amino acid segment at the end of the DNA-binding domain essential for the development of TECs but not keratinocytes. The transcriptional activity of this Foxn1 mutant was partly retained, indicating a region that specifies TEC functions. Analysis of an additional 9 FOXN1 mutations identified in multiple unrelated patients revealed distinct functional consequences contingent on the impact of the mutation on the DNA-binding and transactivation domains of FOXN1.

Introduction: Inflammatory bowel disease (IBD) affects approximately 1/3 of patients with chronic granulomatous disease (CGD). Comprehensive investigation of the effect of allogeneic hematopoietic cell transplantation (HCT) on CGD IBD and the impact of IBD on transplant outcomes is lacking., Methods: We collected data retrospectively from 145 patients with CGD who had received allogeneic HCT at 26 Primary Immune Deficiency Treatment Consortium (PIDTC) centers between January 1, 2005 and June 30, 2016., Results: Forty-nine CGD patients with IBD and 96 patients without IBD underwent allogeneic HCT. Eighty-nine percent of patients with IBD and 93% of patients without IBD engrafted (p = 0.476). Upper gastrointestinal acute GVHD occurred in 8.5% of patients with IBD and 3.5% of patients without IBD (p = 0.246). Lower gastrointestinal acute GVHD occurred in 10.6% of patients with IBD and 11.8% of patients without IBD (p = 0.845). The cumulative incidence of acute GVHD grades II-IV was 30% (CI 17-43%) in patients with IBD and 20% (CI 12-29%) in patients without IBD (p = 0.09). Five-year overall survival was equivalent for patients with and without IBD: 80% [CI 66-89%] and 83% [CI 72-90%], respectively (p = 0.689). All 33 surviving evaluable patients with a history of IBD experienced resolution of IBD by 2 years following allogeneic HCT., Conclusions: In this cohort, allogeneic HCT was curative for CGD-associated IBD. IBD should not contraindicate HCT, as it does not lead to an increased risk of mortality. This study is registered at clinicaltrials.gov NCT02082353.

MicroRNAs (miRNAs) are processed from primary miRNA transcripts (pri-miRNAs), many of which are annotated as long noncoding RNAs (lncRNAs). We assessed whether MIR205HG, the host gene for miR-205, has independent functions as an lncRNA. Comparing mice with targeted deletions of MIR205HG and miR-205 revealed a functional role for the lncRNA in the anterior pituitary. Mice lacking MIR205HG had a temporal reduction in Pit1, growth hormone, and prolactin. This was mediated, in part, through the ability of this lncRNA to bind and regulate the transcriptional activity of Pit1 in conjunction with Zbtb20. Knockdown of MIR205HG in lactotropes decreased the expression of Pit1, Zbtb20, prolactin, and growth hormone, while its overexpression enhanced the levels of these transcripts. The effects of MIR205HG on the pituitary were independent of miR-205. The data support a role for MIR205HG as an lncRNA that regulates growth hormone and prolactin production in the anterior pituitary., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Despite the known importance of zinc for human immunity, molecular insights into its roles have remained limited. Here we report a novel autosomal recessive disease characterized by absent B cells, agammaglobulinemia and early onset infections in five unrelated families. The immunodeficiency results from hypomorphic mutations of SLC39A7, which encodes the endoplasmic reticulum-to-cytoplasm zinc transporter ZIP7. Using CRISPR-Cas9 mutagenesis we have precisely modeled ZIP7 deficiency in mice. Homozygosity for a null allele caused embryonic death, but hypomorphic alleles reproduced the block in B cell development seen in patients. B cells from mutant mice exhibited a diminished concentration of cytoplasmic free zinc, increased phosphatase activity and decreased phosphorylation of signaling molecules downstream of the pre-B cell and B cell receptors. Our findings highlight a specific role for cytosolic Zn 2+ in modulating B cell receptor signal strength and positive selection.

Purpose: Hemophagocytic lymphohistiocytosis (HLH) in adults is rare but frequently fatal. Diagnosis is often delayed and treatment approaches vary significantly in contrast to the protocol-driven approach typically used in pediatric HLH. To improve care of these complex patients, this study retrospectively examined the prevalence, clinical characteristics, therapies and outcomes of adult HLH patients at two large tertiary care centers., Methods: Adult patients with HLH confirmed by retrospective review of electronic medical records using HLH2004 criteria during admissions to the University of Texas Southwestern and Parkland Memorial Hospitals between June 2007 and June 2017 were studied., Results: Of 31 patients included, 67.7% were male with mean age of 46 years. Average time from admission to diagnosis was 10.5 days. 48% of patients had malignancy, with T-cell lymphoma being most common. Infections were seen in 70%. Autoimmune disorders were found in 9.6%. In total, 13 patients survived (44.8%). Median survival was 8 months with increased mortality in malignancy-associated HLH (median 0.56 months versus 36.5 months, p < 0.001). T-cell lymphoma carried a worse prognosis than other malignancies. Central nervous system disease, hypoalbuminemia, elevated bilirubin, elevated soluble interleukin 2 receptor, and elevated lactate dehydrogenase, were also associated with poor survival. Treatment varied significantly. No individual treatment improved survival., Conclusion: This study corroborates prior limited data in adult HLH patients regarding poor survival, particularly in malignancy-associated HLH. Earlier recognition of this disease and a multidisciplinary approach to streamline diagnosis and optimize treatment are needed to improve outcomes in adult HLH patients., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Purpose of Review: Overview of neuroendocrine neoplasms in the context of their associations with primary and secondary immunodeficiency states., Recent Findings: Malignancies of neuroendocrine origin are well known to be associated with hereditary syndromes, including multiple endocrine neoplasia type 1, von Hippel-Lindau syndrome, neurofibromatosis type 1, and tuberous sclerosis. This review includes the X-linked form of hyper-IgM syndrome (XHIGM), due to mutations in the CD40Ligand gene (CD40LG), as an additional inherited disorder with susceptibility to such malignancies, and discusses neuroendocrine tumors (NETs) arising in other immunocompromised states. Of all primary immune deficiency diseases, NETs appear to be unique to XHIGM patients. Outcomes for XHIGM patients with NETs is poor, and the mechanism behind this association remains unclear. In secondary immune deficiency states, NET occurrences were primarily in patients with HIV or AIDS, the autoimmune disease systemic lupus erythematosus and solid organ transplant recipients. Gastroenteropancreatic NETs were most frequent in XHIGM patients, whereas nongastroenteropancreatic-NETs, like Merkel cell carcinoma and small-cell lung carcinoma, affected HIV/AIDS patients. Possible mechanisms as to the nature of these associations are discussed, including chronic infections and inflammation, and CD40-CD40L interactions. Many questions remain, and further studies are needed to clarify the predisposition of patients with XHIGM to the development of NETs. Given that many of these patients present late in their disease state and have poor outcomes, it is imperative to keep a high index of suspicion at the advent of early signs and symptoms. Regular monitoring with laboratory or imaging studies, including tumor markers, may be warranted, for which further studies are needed., Summary: Of all primary immunodeficiency diseases, NETs appear to be unique to XHIGM, and the mechanism behind this association remains unclear. Outcome for XHIGM patients with NETs is poor, and it is imperative to keep a high index of suspicion at the advent of early signs and symptoms.

[This corrects the article on p. 798 in vol. 8, PMID: 28769923.].

NF-κB signaling through its NFKB1 -dependent canonical and NFKB2 -dependent noncanonical pathways plays distinctive roles in a diverse range of immune processes. Recently, mutations in these 2 genes have been associated with common variable immunodeficiency (CVID). While studying patients with genetically uncharacterized primary immunodeficiencies, we detected 2 novel nonsense gain-of-function (GOF) NFKB2 mutations (E418X and R635X) in 3 patients from 2 families, and a novel missense change (S866R) in another patient. Their immunophenotype was assessed by flow cytometry and protein expression; activation of canonical and noncanonical pathways was examined in peripheral blood mononuclear cells and transfected HEK293T cells through immunoblotting, immunohistochemistry, luciferase activity, real-time polymerase chain reaction, and multiplex assays. The S866R change disrupted a C-terminal NF-κΒ2 critical site affecting protein phosphorylation and nuclear translocation, resulting in CVID with adrenocorticotropic hormone deficiency, growth hormone deficiency, and mild ectodermal dysplasia as previously described. In contrast, the nonsense mutations E418X and R635X observed in 3 patients led to constitutive nuclear localization and activation of both canonical and noncanonical NF-κΒ pathways, resulting in a combined immunodeficiency (CID) without endocrine or ectodermal manifestations. These changes were also found in 2 asymptomatic relatives. Thus, these novel NFKB2 GOF mutations produce a nonfully penetrant CID phenotype through a different pathophysiologic mechanism than previously described for mutations in NFKB2 .

Background: X-linked hyper-IgM syndrome (XHIGM) is a primary immunodeficiency with high morbidity and mortality compared with those seen in healthy subjects. Hematopoietic cell transplantation (HCT) has been considered a curative therapy, but the procedure has inherent complications and might not be available for all patients., Objectives: We sought to collect data on the clinical presentation, treatment, and follow-up of a large sample of patients with XHIGM to (1) compare long-term overall survival and general well-being of patients treated with or without HCT along with clinical factors associated with mortality and (2) summarize clinical practice and risk factors in the subgroup of patients treated with HCT., Methods: Physicians caring for patients with primary immunodeficiency diseases were identified through the Jeffrey Modell Foundation, United States Immunodeficiency Network, Latin American Society for Immunodeficiency, and Primary Immune Deficiency Treatment Consortium. Data were collected with a Research Electronic Data Capture Web application. Survival from time of diagnosis or transplantation was estimated by using the Kaplan-Meier method compared with log-rank tests and modeled by using proportional hazards regression., Results: Twenty-eight clinical sites provided data on 189 patients given a diagnosis of XHIGM between 1964 and 2013; 176 had valid follow-up and vital status information. Sixty-seven (38%) patients received HCT. The average follow-up time was 8.5 ± 7.2 years (range, 0.1-36.2 years). No difference in overall survival was observed between patients treated with or without HCT (P = .671). However, risk associated with HCT decreased for diagnosis years 1987-1995; the hazard ratio was significantly less than 1 for diagnosis years 1995-1999. Liver disease was a significant predictor of overall survival (hazard ratio, 4.9; 95% confidence limits, 2.2-10.8; P < .001). Among survivors, those treated with HCT had higher median Karnofsky/Lansky scores than those treated without HCT (P < .001). Among patients receiving HCT, 27 (40%) had graft-versus-host disease, and most deaths occurred within 1 year of transplantation., Conclusion: No difference in survival was observed between patients treated with or without HCT across all diagnosis years (1964-2013). However, survivors treated with HCT experienced somewhat greater well-being, and hazards associated with HCT decreased, reaching levels of significantly less risk in the late 1990s. Among patients treated with HCT, treatment at an early age is associated with improved survival. Optimism remains guarded as additional evidence accumulates., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

The primary immunodeficiency (PID) diseases comprise a heterogeneous group of inherited disorders of immune function. Technical advancements in whole-genome, whole-exome, and RNA-sequencing have seen the explosion of genetic discoveries in the field of PIDs. The present review aims to focus on a group of immunodeficiency disorders associated with elevated levels of IgM (hyper IgM; HIGM) and provides a clinical differential diagnosis. Most patients present for evaluation of immunodeficiency due to recurrent infections, and laboratory studies show either a clear isolated elevation of serum immunoglobulin M (IgM) with low or absent IgG, IgA, and IgE. Alternatively, IgM levels may be normal or moderately elevated while other serum immunoglobulins are reported below the norms for age but not absent. Mechanistically, these disorders are recognized as defects in immunoglobulin (Ig) class switch recombination (CSR). Importantly, to safeguard genetic stability, CSR utilizes elements of the DNA repair machinery including multi-protein complexes involved in mismatch repair (MMR). Therefore, it is not uncommon for defects in the DNA repair machinery, to present with laboratory findings of HIGM. This review will discuss clinical phenotypes associated with congenital defects associated with HIGM. Clinical manifestations, relevant immunologic testing, inheritance pattern, molecular diagnosis, presumed pathogenesis, and OMIM number, when annotated are compiled. Accepted therapeutic options, when available, are reviewed for each condition discussed., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

The thymus, an organ responsible for T cell development, is one of the more stress-sensitive tissues in the body. Stress, in the form of infections, radiation exposure, and steroids, impairs thymic epithelial cell (TEC) functions and induces the programmed cell death of immature thymocytes. MicroRNAs are small noncoding RNAs involved in tissue repair and homeostasis, with several supporting T cell development. We report that miR-205, an epithelial-specific miR, maintains thymopoiesis following inflammatory perturbations. Thus, the activation of diverse pattern recognition receptors in mice causes a more severe thymic hypoplasia and delayed T cell recovery when miR-205 is conditionally ablated in TECs. Gene expression comparisons in the TECs with/without miR-205 revealed a significant differential regulation of chemokine/chemokine receptor pathways, antigen processing components, and changes in the Wnt signaling system. This was partly a consequence of reduced expression of the transcriptional regulator of epithelial cell function, Forkhead Box N1 (Foxn1), and its two regulated targets, stem cell factor and ccl25, following stress. miR-205 mimics supplemented into miR-205-deficient fetal thymic organ cultures restored Foxn1 expression along with ccl25 and stem cell factor A number of putative targets of miR-205 were up-regulated in TECs lacking miR-205, consistent with an important role for this miR in supporting T cell development in response to stress., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

Background: Primary immunodeficiency diseases (PIDDs) are inherited disorders of the immune system. The most severe form, severe combined immunodeficiency (SCID), presents with profound deficiencies of T cells, B cells, or both at birth. If not treated promptly, affected patients usually do not live beyond infancy because of infections. Genetic heterogeneity of SCID frequently delays the diagnosis; a specific diagnosis is crucial for life-saving treatment and optimal management., Objective: We developed a next-generation sequencing (NGS)-based multigene-targeted panel for SCID and other severe PIDDs requiring rapid therapeutic actions in a clinical laboratory setting., Methods: The target gene capture/NGS assay provides an average read depth of approximately 1000×. The deep coverage facilitates simultaneous detection of single nucleotide variants and exonic copy number variants in one comprehensive assessment. Exons with insufficient coverage (<20× read depth) or high sequence homology (pseudogenes) are complemented by amplicon-based sequencing with specific primers to ensure 100% coverage of all targeted regions., Results: Analysis of 20 patient samples with low T-cell receptor excision circle numbers on newborn screening or a positive family history or clinical suspicion of SCID or other severe PIDD identified deleterious mutations in 14 of them. Identified pathogenic variants included both single nucleotide variants and exonic copy number variants, such as hemizygous nonsense, frameshift, and missense changes in IL2RG; compound heterozygous changes in ATM, RAG1, and CIITA; homozygous changes in DCLRE1C and IL7R; and a heterozygous nonsense mutation in CHD7., Conclusion: High-throughput deep sequencing analysis with complete clinical validation greatly increases the diagnostic yield of severe primary immunodeficiency. Establishing a molecular diagnosis enables early immune reconstitution through prompt therapeutic intervention and guides management for improved long-term quality of life., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Aberrant nucleic acids generated during viral replication are the main trigger for antiviral immunity, and mutations that disrupt nucleic acid metabolism can lead to autoinflammatory disorders. Here we investigated the etiology of X-linked reticulate pigmentary disorder (XLPDR), a primary immunodeficiency with autoinflammatory features. We discovered that XLPDR is caused by an intronic mutation that disrupts the expression of POLA1, which encodes the catalytic subunit of DNA polymerase-α. Unexpectedly, POLA1 deficiency resulted in increased production of type I interferons. This enzyme is necessary for the synthesis of RNA:DNA primers during DNA replication and, strikingly, we found that POLA1 is also required for the synthesis of cytosolic RNA:DNA, which directly modulates interferon activation. Together this work identifies POLA1 as a critical regulator of the type I interferon response.

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by a defect in production of phagocyte-derived reactive oxygen species, which leads to recurrent infections with a characteristic group of pathogens not previously known to include methylotrophs. Methylotrophs are versatile environmental bacteria that can use single-carbon organic compounds as their sole source of energy; they rarely cause disease in immunocompetent persons. We have identified 12 infections with methylotrophs (5 reported here, 7 previously reported) in patients with CGD. Methylotrophs identified were Granulibacter bethesdensis (9 cases), Acidomonas methanolica (2 cases), and Methylobacterium lusitanum (1 case). Two patients in Europe died; the other 10, from North and Central America, recovered after prolonged courses of antimicrobial drug therapy and, for some, surgery. Methylotrophs are emerging as disease-causing organisms in patients with CGD. For all patients, sequencing of the 16S rRNA gene was required for correct diagnosis. Geographic origin of the methylotroph strain may affect clinical management and prognosis.

Importance: Newborn screening for severe combined immunodeficiency (SCID) using assays to detect T-cell receptor excision circles (TRECs) began in Wisconsin in 2008, and SCID was added to the national recommended uniform panel for newborn screened disorders in 2010. Currently 23 states, the District of Columbia, and the Navajo Nation conduct population-wide newborn screening for SCID. The incidence of SCID is estimated at 1 in 100,000 births., Objectives: To present data from a spectrum of SCID newborn screening programs, establish population-based incidence for SCID and other conditions with T-cell lymphopenia, and document early institution of effective treatments., Design: Epidemiological and retrospective observational study., Setting: Representatives in states conducting SCID newborn screening were invited to submit their SCID screening algorithms, test performance data, and deidentified clinical and laboratory information regarding infants screened and cases with nonnormal results. Infants born from the start of each participating program from January 2008 through the most recent evaluable date prior to July 2013 were included. Representatives from 10 states plus the Navajo Area Indian Health Service contributed data from 3,030,083 newborns screened with a TREC test., Main Outcomes and Measures: Infants with SCID and other diagnoses of T-cell lymphopenia were classified. Incidence and, where possible, etiologies were determined. Interventions and survival were tracked., Results: Screening detected 52 cases of typical SCID, leaky SCID, and Omenn syndrome, affecting 1 in 58,000 infants (95% CI, 1/46,000-1/80,000). Survival of SCID-affected infants through their diagnosis and immune reconstitution was 87% (45/52), 92% (45/49) for infants who received transplantation, enzyme replacement, and/or gene therapy. Additional interventions for SCID and non-SCID T-cell lymphopenia included immunoglobulin infusions, preventive antibiotics, and avoidance of live vaccines. Variations in definitions and follow-up practices influenced the rates of detection of non-SCID T-cell lymphopenia., Conclusions and Relevance: Newborn screening in 11 programs in the United States identified SCID in 1 in 58,000 infants, with high survival. The usefulness of detection of non-SCID T-cell lymphopenias by the same screening remains to be determined.

Primary immunodeficiencies are intrinsic defects in the immune system that result in a predisposition to infection and are frequently accompanied by a propensity to autoimmunity and/or immunedysregulation. Primary immunodeficiencies can be divided into innate immunodeficiencies, phagocytic deficiencies, complement deficiencies, disorders of T cells and B cells (combined immunodeficiencies), antibody deficiencies and immunodeficiencies associated with syndromes. Diseases of immune dysregulation and autoinflammatory disorder are many times also included although the immunodeficiency in these disorders are often secondary to the autoimmunity or immune dysregulation and/or secondary immunosuppression used to control these disorders. Congenital primary immunodeficiencies typically manifest early in life although delayed onset are increasingly recognized. The early diagnosis of congenital immunodeficiencies is essential for optimal management and improved outcomes. In this International Consensus (ICON) document, we provide the salient features of the most common congenital immunodeficiencies.

Hematopoietic cell transplantation (HCT) is a curative therapeutic option for severe combined immunodeficiency (SCID), a group of diseases which otherwise carry life expectancies that are of limited duration and quality. Survival following HCT for SCID has improved from approximately 23 to 91 % over the last 40 years. Success with SCID prompted efforts to apply HCT to the therapeutic challenge of well over 20 molecularly defined primary immune deficiency diseases (PID). Such success is due to both early recognition of PIDs and advances in the field of transplantation. Such advances include high-resolution HLA DNA donor-recipient matching, expansion of donor sources, better tolerated conditioning, new antibiotics, and wider availability. International collaborative efforts have provided patients and caregivers information that permit better treatment decisions now, and direct clinicians and investigators to ensure progress in the future. Pioneers in screening for SCID have taken steps to correct the fundamental challenge to successful treatment, which is the rapid discovery and characterization of cases and offering the transplant option to an affected child early in life; blood spot testing for T and B cell receptor quantification is now available to a growing fraction of newborns. Organizations including the Primary Immune Deficiency Treatment Consortium in the USA, The European Society for Primary Immunodeficiency, the European Group for Blood and Marrow Transplantation, the Pediatric Blood and Marrow Transplant Consortium, the United States Immunodeficiency Network, the Immune Deficiency Foundation, and the Jeffrey Modell Foundation are contributing mightily to increase awareness and standardize optimal utilization to the benefit of patients. This review will update the allergist-immunologist concerning disease presentations, indications for transplantation, methodologies, conditioning regimens, and clinical outcomes for patients with PID for which timely HCT is critical.

Long-term prophylactic antibiotics are being widely implemented as primary or adjunctive therapy in primary immune deficiencies. This practice has transformed clinical outcomes in the setting of chronic granulomatous disease, complement deficiencies, Mendelian susceptibility to mycobacterial disease, Wiskott-Aldrich syndrome, hyper-IgE syndrome, Toll signaling defects, and prevented Pneumocystis in patients with T-cell deficiencies. Yet, controlled trials are few in the context of primary antibody deficiency syndromes, and most of this practice has been extrapolated from data in patients who are immune competent and with recurrent acute otitis media, chronic rhinosinusitis, cystic fibrosis, and bronchiectasis. The paucity of guidelines on the subject is reflected in recent surveys among practicing immunologists that highlight differences of habit regarding this treatment. Such discrepancies reinforce the lack of standard protocols on the subject. This review will provide evidence for the use of antibiotic prophylaxis in various primary immune deficiency populations, especially highlighting the role antibiotic prophylaxis in primary antibody deficiency syndromes. We also discussed the relationship of long-term antibiotic use and the prevalence of resistant pathogens. Overall, examination of available data on the use of prophylactic antibiotics in antibody deficiency syndromes merit future investigation in well-designed multicenter prospective trials because this population has few other management options., (Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

miR-185 is a microRNA (miR) that targets Bruton's tyrosine kinase in B cells, with reductions in miR-185 linked to B cell autoantibody production. In hippocampal neurons, miR-185 targets both sarcoplasmic/endoplasmic reticulum calcium ATPase 2 and a novel Golgi inhibitor. This miR is haploinsufficient in 90-95% of individuals with chromosome 22q11.2 deletion syndrome, patients who can present with immune, cardiac, and parathyroid problems, learning disorders, and a high incidence of schizophrenia in adults. The reduced levels of miR-185 in neurons cause presynaptic neurotransmitter release. Many of the 22q11.2 deletion syndrome patients have a thymic hypoplasia, which results in a peripheral T cell lymphopenia and unusual T helper cell skewing. The molecular targets of miR-185 in thymocytes are unknown. Using an miR-185 T cell transgenic approach, increasing levels of miR-185 attenuated T cell development at the T cell receptor β (TCRβ) selection checkpoint and during positive selection. This caused a peripheral T cell lymphopenia. Mzb1, Nfatc3, and Camk4 were identified as novel miR-185 targets. Elevations in miR-185 enhanced TCR-dependent intracellular calcium levels, whereas a knockdown of miR-185 diminished these calcium responses. These effects concur with reductions in Mzb1, an endoplasmic reticulum calcium regulator. Consistent with their haploinsufficiency of miR-185, Mzb1 levels were elevated in thymocyte extracts from several 22q11.2 deletion syndrome patients. Our findings indicate that miR-185 regulates T cell development through its targeting of several mRNAs including Mzb1.

Patients with 22q11.2 deletion syndrome have heterogeneous clinical presentations including immunodeficiency, cardiac anomalies, and hypocalcemia. The syndrome arises from hemizygous deletions of up to 3Mb on chromosome 22q11.2, a region that contains 60 genes and 4 microRNAs. MicroRNAs are important post-transcriptional regulators of gene expression, with mutations in several microRNAs causal to specific human diseases. We characterized the microRNA expression patterns in the peripheral blood of patients with 22q11.2 deletion syndrome (n=31) compared to normal controls (n=22). Eighteen microRNAs had a statistically significant differential expression (p<0.05), with miR-185 expressed at 0.4× normal levels. The 22q11.2 deletion syndrome cohort exhibited microRNA expression hyper-variability and group dysregulation. Selected microRNAs distinguished patients with cardiac anomalies, hypocalcemia, and/or low circulating T cell counts. In summary, microRNA profiling of chromosome 22q11.2 deletion syndrome/DiGeorge patients revealed a signature microRNA expression pattern distinct from normal controls with clinical relevance., (Copyright © 2013 Elsevier Inc. All rights reserved.)

In tonsils, CD138(+) plasma cells (PCs) are surrounded by CD163(+) resident macrophages (Ms). We show here that human Ms (isolated from tonsils or generated from monocytes in vitro) drive activated B cells to differentiate into CD138(+)CD38(++) PCs through secreted CXCL10/IP-10 and VCAM-1 contact. IP-10 production by Ms is induced by B cell-derived IL-6 and depends on STAT3 phosphorylation. Furthermore, IP-10 amplifies the production of IL-6 by B cells, which sustains the STAT3 signals that lead to PC differentiation. IP-10-deficient mice challenged with NP-Ficoll show a decreased frequency of NP-specific PCs and lower titers of antibodies. Thus, our results reveal a novel dialog between Ms and B cells, in which IP-10 acts as a PC differentiation factor.

The last 40 years has seen the emergence of hematopoietic stem cell transplantation as a therapeutic modality for fatal diseases and as a curative option for individuals born with inherited disorders that carry limited life expectancy and poor quality of life. Despite the rarity of many primary immunodeficiency diseases, these disorders have led the way toward innovative therapies and further provide insights into mechanisms of immunologic reconstitution applicable to all hematopoietic stem cell transplants. This article represents a historical perspective of the early investigators and their contributions. It also reviews the parallel work that oncologists and immunologists have undertaken to treat both primary immunodeficiencies and hematologic malignancies., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Physiological stress evokes rapid changes in both the innate and adaptive immune response. Immature αβ T cells developing in the thymus are particularly sensitive to stress, with infections and/or exposure to lipopolysaccharide or glucocorticoids eliciting a rapid apoptotic program. MicroRNAs are a class of small, non-coding RNAs that regulate global gene expression by targeting diverse mRNAs for degradation. We hypothesized that a subset of thymically encoded microRNAs would be stress responsive and modulate thymopoiesis. We performed microRNA profiling of thymic microRNAs isolated from control or stressed thymic tissue obtained from mice. We identified 18 microRNAs that are dysregulated >1.5-fold in response to lipopolysaccharide or the synthetic corticosteroid dexamethasone. These included the miR-17-90 cluster, which have anti-apoptotic functions, and the miR-181 family, which contribute to T cell tolerance. The stress-induced changes in the thymic microRNAs are dynamically and distinctly regulated in the CD4(-)CD8(-), CD4(+)CD8(+), CD4(+)CD8(-), and CD4(-)CD8(+) thymocyte subsets. Several of the differentially regulated murine thymic miRs are also stress responsive in the heart, kidney, liver, brain, and/or spleen. The most dramatic thymic microRNA down modulated is miR-181d, exhibiting a 15-fold reduction following stress. This miR has both similar and distinct gene targets as miR-181a, another member of miR-181 family. Many of the differentially regulated microRNAs have known functions in thymopoiesis, indicating that their dysregulation will alter T cell repertoire selection and the formation of naïve T cells. This data has implications for clinical treatments involving anti-inflammatory steroids, ablation therapies, and provides mechanistic insights into the consequences of infections.

Introduction: We describe a previously unreported 437 T→G missense mutation producing a V146G substitution in the first coiled-coil (CC1) domain of nuclear factor-κB essential modulator (NEMO) in a 9-month-old boy with ectodermal dysplasia with immunodeficiency who presented with methicillin-resistant Staphylococcus aureus subdural empyema. We performed in vitro experiments to determine if this novel mutation resulted in impaired NF-κB signaling., Methods: IκBα phosphorylation experiments were performed using a Jurkat T cell line lacking endogenous NEMO expression that was transfected with vectors containing either the wild type or the patient's V146G mutation. The cells were stimulated with TNF-α to activate the NF-κB pathway. Phosphorylated IκBα was detected by immunoblotting with anti-phospho-IκBα antibodies. Peripheral blood mononuclear cells from the patient were stimulated with TNF-α or anti-CD3 and anti-CD28. Impaired IκBα degradation was detected using antibodies against the IκBα protein., Results: While TNF-α stimulation resulted in IκBα phosphorylation in NEMO-deficient Jurkat cells reconstituted with wild-type NEMO, cell transfected with the V146G mutant exhibited a 75% reduction in phospho-IκBα. Peripheral blood mononuclear cells from the patient showed impaired degradation of IκBα after stimulation when compared with normal controls., Conclusions: The patient's V146G mutation results in impaired NF-κB activation in vitro. The mutation extends the known N-terminal boundary within the CC1 domain that produces an ectodermal dysplasia phenotype, and defines an infectious susceptibility previously unappreciated in ectodermal dysplasia with immunodeficiency (methicillin-resistant S. aureus subdural empyema), broadening the clinical spectrum associated with the disease.