Insights into immunity from clinical and basic science studies of DOCK8 immunodeficiency syndrome

Periodontal Status and Herpesiviridae, Bacteria, and Fungi in Gingivitis and Periodontitis of Systemically Compromised Pediatric Subjects: A Systematic Review

BACKGROUND

Gingivitis and periodontitis are microbially associated diseases, with some features characteristic of pediatric age and others linked to systemic diseases. While the role of periodontal pathogenic bacteria is well recognized, the contribution of fungi and viruses, particularly Herpesviridae, remains controversial. Studies in adults have highlighted the presence of Herpesviridae, but evidence in pediatric subjects, especially systemically compromised, is limited. This systematic review aimed to assess periodontal status (e.g., health, gingivitis, periodontitis, necrotizing gingivitis, and/or periodontitis) and the subgingival and/or salivary microbial (bacterial, viral, and fungal) profile in systemically compromised pediatric (≤18 years) subjects with gingivitis and/or periodontitis compared to clinical periodontal health.

METHODS

The review protocol was registered on PROSPERO (CRD42024597695) and followed the PRISMA statement. Data from eight studies were descriptively analyzed and qualitatively assessed through ROBINS-I and JBI tools.

RESULTS

CMV was frequently detected, particularly in necrotizing gingivitis (19.40%). EBV was found in necrotizing gingivitis (20.69%) and periodontitis (10.34%); HSV was mainly associated with gingivitis and necrotizing gingivitis. Bacteria species in periodontitis included Porphyromonas gingivalis, Tannerella forsythia, Fusobacterium, and Campylobacter species. Candida albicans was detected in periodontitis, suggesting a fungal involvement in the disease's pathogenesis. Although the bacterial and fungal profile was not investigated, limited viral presence was noted in subjects with healthy periodontium, indicating a stable microbiome.

CONCLUSIONS

These findings underscore the dynamics of microbial interactions in the progression of periodontal disease in systemically compromised pediatric subjects.

Role of DOCK8 in cytokine storm syndromes

BACKGROUND

Cytokine storm syndromes (CSSs), including hemophagocytic lymphohistiocytosis (HLH), are increasingly recognized as hyperinflammatory states leading to multiorgan failure and death. Familial HLH in infancy results from homozygous genetic defects in perforin-mediated cytolysis by CD8 T lymphocytes and natural killer (NK) cells. Later-onset CSSs are often associated with heterozygous defects in familial HLH genes, but genetic etiologies for most are unknown. We identified rare dedicator of cytokinesis 8 (DOCK8) variants in patients with CSS.

OBJECTIVE

We sought to explore the role of CSS patient-derived DOCK8 mutations on cytolytic activity in NK cells and to further study effects of DOCK8 deficiency in murine models of CSSs.

METHODS

DOCK8 cDNAs from 2 unrelated patients with CSS with different missense mutations were introduced into human NK-92 cells by foamy virus transduction. NK-cell degranulation (CD107a), cytolytic activity against K562 target cells, and IFN-γ production were explored by flow cytometry. A third patient with CSS with DOCK8 mRNA splice acceptor site variant was explored by exon trapping. Dock8-/- mice were assessed for features of CSS (weight loss, splenomegaly, hepatic inflammation, cytopenias, and IFN-γ levels) on challenge with lymphocytic choriomeningitis virus and excess IL-18.

RESULTS

Both patient DOCK8 missense mutations decreased cytolytic function in NK cells in a partial dominant-negative fashion in vitro. The patient DOCK8 splice variant disrupted mRNA splicing in vitro. Lymphocytic choriomeningitis virus infection promoted CSS in Dock8-/- mice and interacted with excess IL-18, limiting T-cell numbers while promoting CD8 T-cell hyperactivation.

CONCLUSIONS

Mutations in DOCK8 may contribute to CSS-like hyperinflammatory states by altering cytolytic function in a threshold model of disease.

Case report: Advanced age at transplantation and pre-emptive treatment with dupilumab in DOCK8 deficiency

Dedicator of cytokinesis 8 (DOCK8) deficiency is a combined immunodeficiency (CID) due to biallelic mutations in the gene encoding DOCK8. Major clinical phenomena are recurrent severe infections of the lungs and skin, atopic eczema, and predisposition to malignancy leading to a poor prognosis. Typical findings include highly elevated IgE and eosinophilia. Allogeneic hematopoietic stem cell transplantation (alloHSCT) is indicated as the only curative treatment option. We present a patient with advanced disease undergoing alloHSCT at the age of 11 years after individualized pre-treatment using dupilumab and rituximab resulting in a decrease in IgE levels and clinical improvement of the skin condition. Additionally, in a review of the literature, we summarize morbidity and outcome in DOCK8-deficient patients older than 8 years of age receiving alloHSCT. Life-threatening infections, malignancy, and disease-related complications with organ damage pre-transplant are challenging in older DOCK8-deficient patients. The therapeutic role of dupilumab in DOCK8 deficiency should be evaluated in larger studies.

Hematopoietic cell transplantation for DOCK8 deficiency: Results from a prospective clinical trial

BACKGROUND

DOCK8 deficiency is a primary immunodeficiency in which allogeneic hematopoietic cell transplantation (HCT) represents the only known cure. We tested the ability of a busulfan-based regimen to achieve reliable engraftment and high levels of donor chimerism with acceptable toxicity in a prospective clinical trial in DOCK8 deficiency.

OBJECTIVES

To both evaluate the ability of HCT to reverse the clinical phenotype and to correct the immunologic abnormalities by 1 year post HCT.

METHODS

We conducted a prospective HCT trial for recipients with DOCK8 deficiency. Subjects were recruited from October 5, 2010, to December 30, 2022. Donor sources included fully matched related and unrelated donors and haploidentical donors. The reduced toxicity, myeloablative conditioning regimen contained no serotherapy. Graft-versus-host disease (GVHD) prophylaxis included either a calcineurin inhibitor with methotrexate or post-HCT cyclophosphamide (PT/Cy) followed by tacrolimus and mycophenolate mofetil. The trial was later amended to study PT/Cy in all patients. (Pilot Study of Reduced-Intensity Hematopoietic Stem Cell Transplant of DOCK8 [NCT01176006].) RESULTS: Thirty-six subjects, both children and adults (median age 16.4 years), underwent HCT for DOCK8 deficiency. Most patients, 33 of 36 (92%), achieved full (≥98%) donor chimerism in whole blood as early as day +30. With a median potential follow-up of 7.4 years, 29 (80.6%) were alive with no evidence of new DOCK8 deficiency-related complications. PT/Cy was effective in reducing the risk of acute GVHD in patients who had received matched unrelated donor and haploidentical transplants, but it was associated with transient delays in immune-reconstitution and hemorrhagic cystitis.

CONCLUSIONS

A busulfan-based HCT regimen using PT/Cy for GVHD prophylaxis and a broad range of donor types and hematopoietic cell sources were well tolerated, leading to the reversal of the clinical immunophenotype.

T follicular helper cells in food allergy

T follicular helper (Tfh) cells help direct the production of antibodies by B cells. In addition to promoting antibody responses to vaccination and infection, Tfh cells have been found to mediate antibody production to food antigens. Work over the past decade has delineated the specific phenotypes of Tfh cells that induce antibodies to food while also clarifying the divergent Tfh cell requirement for different food-specific antibody isotypes. Furthermore, Tfh and antibody responses to food can occur at multiple barrier sites - namely, skin, airway, and gut. Depending on the context of food antigen exposure, the immune response to food at these sites can be protective, as in the case of tolerance or immunotherapy, or pathogenic, as in the case of allergy. This review will highlight recent advances in our understanding of how Tfh cells promote antibodies to food as well as future avenues for continued discovery.

DOCK8 deficiency due to a deep intronic variant in two kindreds with hyper-IgE syndrome

Dedicator of cytokinesis 8 (DOCK8) deficiency underlies the majority of cases of patients with autosomal recessive form of the hyper-immunoglobulin E syndrome (HIES). Most DOCK8 mutations involve deletions and splice junction mutations that abrogate protein expression. However, a few patients whose presentation is reminiscent of DOCK8 deficiency have no identifiable mutations. Using Whole Exome Sequencing (WES), we identified a deep intronic homozygous DOCK8 variant located in intron 36 (c.4626 + 76 A > G) in two unrelated patients with features of HIES that resulted in an in-frame 75 base pair intronic sequence insertion in DOCK8 cDNA, resulting in a premature stop codon (p.S1542ins6Ter). This variant resulted in variable decrease in DOCK8 expression that was associated with impaired T cell receptor-triggered actin polymerization, decreased IL-6-induced STAT3 phosphorylation, reduced expression of the Th17 cell markers CCR6 and IL-17, and higher frequencies of GATA3+ T cells indicative of Th2 skewing. Our approach extends the reach of WES in identifying disease-related intronic variants. It highlights the role of non-coding mutations in immunodeficiency disorders, including DOCK8 deficiency, and emphasizes the need to explore these mutations in unexplained inborn errors of immunity.

Dedicator of cytokinesis 8 (DOCK8) mutation impairs the differentiation of helper T cells by regulating the glycolytic pathway of CD4+ T cells

Dedicator of cytokinesis 8 (DOCK8) deficiency is a primary immunodeficiency disease caused by mutations in exon 45 of the DOCK8 gene. The clinical signs primarily consist of increased serum IgE levels, eczema, repeated skin infections, allergies, and upper respiratory tract infections. Using CRISPR/Cas9 technology, we generated a DOCK8 exon 45 mutation in mice, mirroring the mutation found in patients. The results indicated that DOCK8 mutation impairs peripheral T cell homeostasis, disrupts regulatory T cells (Tregs) development, increases ICOS expression in Tregs within peripheral lymph nodes (pLn), and promotes Th17 cell differentiation within the spleen and pLn. Upon virus infection, DOCK8 mutation CD4+ T cells have a Th2 effector fate. RNA-bulk sequencing data revealed alternations in the mTOR pathway of DOCK8 mutant CD4+ T cells. We observed that DOCK8 mutation upregulates the glycolysis levels in CD4+ T cells, which is related to the Akt/mTOR/S6/HIF-1α pathway. In summary, our research elucidates that DOCK8 regulates the differentiation of helper T cells by modulating the glycolytic pathway in CD4+ T cells, thereby advancing the comprehension and offering potential treatment of diseases in DOCK8-deficient patients.

A Novel Case of IFNAR1 Deficiency Identified a Common Canonical Splice Site Variant in DOCK8 in Western Polynesia: The Importance of Validating Variants of Unknown Significance in Under-Represented Ancestries

Advanced genomic technologies such as whole exome or whole genome sequencing have improved diagnoses and disease outcomes for individuals with genetic diseases. Yet, variants of unknown significance (VUS) require rigorous validation to establish disease causality or modification, or to exclude them from further analysis. Here, we describe a young individual of Polynesian ancestry who in the first 13 mo of life presented with SARS-CoV-2 pneumonia, severe enterovirus meningitis and adenovirus gastroenteritis, and severe adverse reaction to MMR vaccination. Genomic analysis identified a previously reported pathogenic homozygous variant in IFNAR1 (c.1156G > T, p.Glu386* LOF), which is common in Western Polynesia. Moreover, a new and putatively deleterious canonical splice site variant in DOCK8 was also found in homozygosity (c.3234 + 2T > C). This DOCK8 variant is common in Polynesians and other under-represented ancestries in large genomic databases. Despite in silico bioinformatic predictions, extensive in vitro and ex vivo analysis revealed the DOCK8 variant likely be neutral. Thus, our study reports a novel case of IFNAR1 deficiency, but also highlights the importance of functional validation of VUS, including those predicted to be deleterious, and the pressing need to expand our knowledge of the genomic architecture and landscape of under-represented populations and ancestries.

Viral infections and inborn errors of immunity

PURPOSE OF REVIEW

The purpose of this focused review is to discuss unusual presentations of viral infections in the context of specific inborn errors of immunity. We will discuss hyper immunoglobulin E (IgE) syndromes, epidermodysplasia verruciformis, and X-linked agammaglobulinemia as examples of inborn errors of immunity associated with specific presentations of viral infection and disease.

RECENT FINDINGS

Advances in both genetic and viral diagnostics have broadened our understanding of viral pathogenesis in the setting of immune dysfunction and the variable phenotype of inborn errors of immunity. Dedicator of cytokinesis 8 (DOCK8) deficiency is now recognized as an inborn error of immunity within the hyper IgE syndrome phenotype and is associated with unusually aggressive cutaneous disease caused by herpes simplex and other viruses. Studies of patients with epidermodysplasia verruciformis have proven that rarely detected human papillomavirus subtypes may cause malignancy in the absence of adequate host defenses. Finally, patients with X-linked agammaglobulinemia may remain at risk for severe and chronic viral infections, even as immune globulin supplementation reduces the risk of bacterial infection.

SUMMARY

Susceptibility to viral infections in patients with inborn errors of immunity is conferred by specific, molecular defects. Recurrent, severe, or otherwise unusual presentations of viral disease should prompt investigation for an underlying genetic defect.

Successfully treated with siltuximab and prednisone in a 7-year-old girl with DOCK8-deficiency presenting as recurrent wart-like lesions: a case report

Dedicator of cytokinesis 8 (DOCK8) deficiency represents a primary immunodeficiency with a wide range of clinical symptoms, including recurrent infections, atopy, and increased malignancy risk. This study presents a case of a 6-year-old girl with DOCK8 deficiency, characterized by severe, treatment-resistant herpetic infections who was successfully treated with siltuximab and glucocorticoids. The successful use of siltuximab in achieving remission highlights the pivotal role of interleukin-6 (IL-6) in DOCK8 deficiency pathogenesis and suggests that IL-6 modulation can be critical in managing DOCK8 deficiency-related viral infections, which may inform future therapeutic strategies for DOCK8 deficiency and similar immunodeficiencies.

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.

Expression profiles of circular RNAs and interaction networks of competing endogenous RNAs in neurogenic bladder of rats following suprasacral spinal cord injury

Background

Neurogenic bladder (NB) following suprasacral spinal cord injury (SSCI) is an interstitial disease with the structural remodeling of bladder tissue and matrix over-deposition. Circular RNAs (circRNAs) are involved in fibrotic disease development through their post-transcriptional regulatory functions. This study aimed to use transcriptome high-throughput sequencing to investigate the process of NB and bladder fibrosis after SSCI.

Methods

Spinal cord transection at the T10-T11 level was used to construct the SSCI model in rats (10-week-old female Wistar rats, weighing 200 ± 20 g). The bladders were collected without (sham group) and with (SSCI 1-3 groups) NB status. Morphological examination was conducted to assess the extent of bladder fibrosis. Additionally, RNA sequencing was utilized to determine mRNAs and circRNAs expression patterns. The dynamic changes of differentially expressed mRNAs (DEMs) and circRNAs (DECs) in different periods of SSCI were further analyzed.

Results

Bladder weight, smooth muscle cell hypertrophy, and extracellular matrix gradually increased after SSCI. Compared with the sham group, 3,255 DEMs and 1,339 DECs, 3,449 DEMs and 1,324 DECs, 884 DEMs, and 1,151 DECs were detected in the SSCI 1-3 groups, respectively. Specifically, circRNA3621, circRNA0617, circRNA0586, and circRNA4426 were significant DECs common to SSCI 1-3 groups compared with the sham group. Moreover, Gene Ontology (GO) enrichment suggested that inflammatory and chronic inflammatory responses were the key events in NB progression following SSCI. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment associated with the "Chemokine signaling pathway", the "IL-17 signaling pathway", and the "TGF-beta signaling pathway" suggests their potential involvement in regulating biological processes. The circRNA-miRNA-mRNA interaction networks of DECs revealed rno-circ-2239 (micu2) as the largest node, indicating that the rno-circ-2239-miRNA-mRNA-mediated network may play a critical role in the pathogenesis of SSCI-induced NB.

Conclusions

This study offers a comprehensive outlook on the possible roles of DEMs and DECs in bladder fibrosis and NB progression following SSCI. These findings have the potential to serve as novel biomarkers and therapeutic targets.

Mapping the splicing landscape of the human immune system

Most human genes code for more than one transcript. Different ratios of transcripts of the same gene can be found in different cell types or states, indicating differential use of transcription start sites or differential splicing. Such differential transcript use (DTUs) events provide an additional layer of regulation and protein diversity. With the exceptions of PTPRC and CIITA, there are very few reported cases of DTU events in the immune system. To rigorously map DTUs between different human immune cell types, we leveraged four publicly available RNA sequencing datasets. We identified 282 DTU events between five human healthy immune cell types that appear in at least two datasets. The patterns of the DTU events were mostly cell-type-specific or lineage-specific, in the context of the five cell types tested. DTUs correlated with the expression pattern of potential regulators, namely, splicing factors and transcription factors. Of the several immune related conditions studied, only sepsis affected the splicing of more than a few genes and only in innate immune cells. Taken together, we map the DTUs landscape in human peripheral blood immune cell types, and present hundreds of genes whose transcript use changes between cell types or upon activation.

The Th17/IL-17 Axis and Host Defense Against Fungal Infections

Chronic mucocutaneous candidiasis (CMC) was recognized as a primary immunodeficiency in the early 1970s. However, for almost 40 years, its genetic etiology remained unknown. The progressive molecular and cellular description of inborn errors of immunity (IEI) with syndromic CMC pointed toward a possible role of IL-17-mediated immunity in protecting against fungal infection and CMC. Since 2011, novel IEI affecting either the response to or production of IL-17A and/or IL-17F (IL-17A/F) in patients with isolated or syndromic CMC provided formal proof of the pivotal role of the IL-17 axis in mucocutaneous immunity to Candida spp, and, to a lesser extent, to Staphylococcus aureus in humans. In contrast, IL-17-mediated immunity seems largely redundant against other common microbes in humans. In this review, we outline the current knowledge of IEI associated with impaired IL-17A/F-mediated immunity, highlighting our current understanding of the role of IL-17A/F in human immunity.

Inborn Errors of Immunity: A Role for Functional Testing and Flow Cytometry in Aiding Clinical Diagnosis

With the exponential discovery of new inborn errors of immunity (IEI), it is becoming increasingly difficult to differentiate between a number of the more recently defined disorders. This is compounded by the fact that although IEI primarily present with immunodeficiency, the spectrum of disease is broad and often extends to features typical of autoimmunity, autoinflammation, atopic disease, and/or malignancy. Here we use case studies to discuss the laboratory and genetic tests used that ultimately led to the specific diagnoses.

[Combined immunodeficiency due to DOCK8 deficiency. State of the art]

Combinedimmunodeficiency (CID) due to DOCK8 deficiency is an inborn error of immunity (IBD) characterized by dysfunctional T and B lymphocytes; The spectrum of manifestations includes allergy, autoimmunity, inflammation, predisposition to cancer, and recurrent infections. DOCK8 deficiency can be distinguished from other CIDs or within the spectrum of hyper-IgE syndromes by exhibiting profound susceptibility to viral skin infections, associated skin cancers, and severe food allergies. The 9p24.3 subtelomeric locus where DOCK8 is located includes numerous repetitive sequence elements that predispose to the generation of large germline deletions and recombination-mediated somatic DNA repair. Residual production DOCK8 protein contributes to the variable phenotype of the disease. Severe viral skin infections and varicella-zoster virus (VZV)-associated vasculopathy, reflect an essential role of the DOCK8 protein, which is required to maintain lymphocyte integrity as cells migrate through the tissues. Loss of DOCK8 causes immune deficiencies through other mechanisms, including a cell survival defect. In addition, there are alterations in the response of dendritic cells, which explains susceptibility to virus infection and regulatory T lymphocytes that could help explain autoimmunity in patients. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment; it improves eczema, allergies, and susceptibility to infections.

Hyper-IgE syndrome caused by DOCK8 mutation with a tumour-like lesion of the lip: a case report

Autosomal recessive hyper-IgE syndrome caused by DOCK8 gene mutation is an immunodeficiency. However, the presentation of a tumour-like lesion of the lip in autosomal recessive hyper-IgE syndrome has not yet been reported. This article reports the case of a 20-year-old man with autosomal recessive hyper-IgE syndrome who presented with a tumour-like lesion of the lip, and hyperplasia and erosion of the gingiva. The clinical manifestations included coarse face and neck skin, a diffuse tumour-like lesion on the upper lip showing a reddish erosive nodular surface with yellowish-white exudation, erosive buccal mucosa, and severe periodontitis. The swollen gingival and palatal mucosa indicated nodular hyperplasia and redness with pseudomembrane. The patient had a significantly increased peripheral blood eosinophil count and serum IgE level and an abnormal T lymphocyte count. His oral lesions improved markedly after prednisolone acetate use and local symptomatic treatment for 2 years. However, the patient unfortunately died of a cerebral infection 6 months after the oral lesions had resolved. The novel features of the labial tumour-like lesion described here extend our understanding of the manifestations of autosomal recessive hyper-IgE syndrome.

CRISPR/Cas-Based Gene Editing Strategies for DOCK8 Immunodeficiency Syndrome

Defects in the DOCK8 gene causes combined immunodeficiency termed DOCK8 immunodeficiency syndrome (DIDS). DIDS previously belonged to the disease category of autosomal recessive hyper IgE syndrome (AR-HIES) but is now classified as a combined immunodeficiency (CID). This genetic disorder induces early onset of susceptibility to severe recurrent viral and bacterial infections, atopic diseases and malignancy resulting in high morbidity and mortality. This pathological state arises from impairment of actin polymerization and cytoskeletal rearrangement, which induces improper immune cell migration-, survival-, and effector functions. Owing to the severity of the disease, early allogenic hematopoietic stem cell transplantation is recommended even though it is associated with risk of unintended adverse effects, the need for compatible donors, and high expenses. So far, no alternative therapies have been developed, but the monogenic recessive nature of the disease suggests that gene therapy may be applied. The advent of the CRISPR/Cas gene editing system heralds a new era of possibilities in precision gene therapy, and positive results from clinical trials have already suggested that the tool may provide definitive cures for several genetic disorders. Here, we discuss the potential application of different CRISPR/Cas-mediated genetic therapies to correct the DOCK8 gene. Our findings encourage the pursuit of CRISPR/Cas-based gene editing approaches, which may constitute more precise, affordable, and low-risk definitive treatment options for DOCK8 deficiency.

Oral anaphylaxis to peanut in a mouse model is associated with gut permeability but not with Tlr4 or Dock8 mutations

BACKGROUND

The etiology of food allergy is poorly understood; mouse models are powerful systems to discover immunologic pathways driving allergic disease. C3H/HeJ mice are a widely used model for the study of peanut allergy because, unlike C57BL/6 or BALB/c mice, they are highly susceptible to oral anaphylaxis. However, the immunologic mechanism of this strain's susceptibility is not known.

OBJECTIVE

We aimed to determine the mechanism underlying the unique susceptibility to anaphylaxis in C3H/HeJ mice. We tested the role of deleterious Toll-like receptor 4 (Tlr4) or dedicator of cytokinesis 8 (Dock8) mutations in this strain because both genes have been associated with food allergy.

METHODS

We generated C3H/HeJ mice with corrected Dock8 or Tlr4 alleles and sensitized and challenged them with peanut. We then characterized the antibody response to sensitization, anaphylaxis response to both oral and systemic peanut challenge, gut microbiome, and biomarkers of gut permeability.

RESULTS

In contrast to C3H/HeJ mice, C57BL/6 mice were resistant to anaphylaxis after oral peanut challenge; however, both strains undergo anaphylaxis with intraperitoneal challenge. Restoring Tlr4 or Dock8 function in C3H/HeJ mice did not protect from anaphylaxis. Instead, we discovered enhanced gut permeability resulting in ingested allergens in the bloodstream in C3H/HeJ mice compared to C57BL/6 mice, which correlated with an increased number of goblet cells in the small intestine.

CONCLUSIONS

Our work highlights the potential importance of gut permeability in driving anaphylaxis to ingested food allergens; it also indicates that genetic loci outside of Tlr4 and Dock8 are responsible for the oral anaphylactic susceptibility of C3H/HeJ mice.

Hyper-IgE Syndrome due to an Elusive Novel Intronic Homozygous Variant in DOCK8

Rare, biallelic loss-of-function mutations in DOCK8 result in a combined immune deficiency characterized by severe and recurrent cutaneous infections, eczema, allergies, and susceptibility to malignancy, as well as impaired humoral and cellular immunity and hyper-IgE. The advent of next-generation sequencing technologies has enabled the rapid molecular diagnosis of rare monogenic diseases, including inborn errors of immunity. These advances have resulted in the implementation of gene-guided treatments, such as hematopoietic stem cell transplant for DOCK8 deficiency. However, putative disease-causing variants revealed by next-generation sequencing need rigorous validation to demonstrate pathogenicity. Here, we report the eventual diagnosis of DOCK8 deficiency in a consanguineous family due to a novel homozygous intronic deletion variant that caused aberrant exon splicing and subsequent loss of expression of DOCK8 protein. Remarkably, the causative variant was not initially detected by clinical whole-genome sequencing but was subsequently identified and validated by combining advanced genomic analysis, RNA-seq, and flow cytometry. This case highlights the need to adopt multipronged confirmatory approaches to definitively solve complex genetic cases that result from variants outside protein-coding exons and conventional splice sites.

Case Report: Fatal Complications of BK Virus-Hemorrhagic Cystitis and Severe Cytokine Release Syndrome Following BK Virus-Specific T-Cells

BK virus (BKV)-hemorrhagic cystitis (HC) is a well-known and rarely fatal complication of hematopoietic stem cell transplantation (HSCT). Treatment for BKV-HC is limited, but virus-specific T-cells (VST) represent a promising therapeutic option feasible for use posttransplant. We report on the case of a 16-year-old male with dedicator of cytokinesis 8 (DOCK8) deficiency who underwent haploidentical HSCT complicated by severe BKV-HC, catastrophic renal hemorrhage, and VST-associated cytokine release syndrome (CRS). Gross hematuria refractory to multiple interventions began with initiation of posttransplant cyclophosphamide (PT/Cy). Complete left renal arterial embolization (day +43) was ultimately indicated to control intractable renal hemorrhage. Subsequent infusion of anti-BK VSTs was complicated by CRS and progressive multiorgan failure, with postmortem analysis confirming diagnosis of hepatic sinusoidal obstruction syndrome (SOS). This case illustrates opportunities for improvement in the management of severe BKV-HC posttransplant while highlighting rare and potentially life-threatening complications of BKV-HC and VST therapy.

Molecular Tuning of Actin Dynamics in Leukocyte Migration as Revealed by Immune-Related Actinopathies

Motility is a crucial activity of immune cells allowing them to patrol tissues as they differentiate, sample or exchange information, and execute their effector functions. Although all immune cells are highly migratory, each subset is endowed with very distinct motility patterns in accordance with functional specification. Furthermore individual immune cell subsets adapt their motility behaviour to the surrounding tissue environment. This review focuses on how the generation and adaptation of diversified motility patterns in immune cells is sustained by actin cytoskeleton dynamics. In particular, we review the knowledge gained through the study of inborn errors of immunity (IEI) related to actin defects. Such pathologies are unique models that help us to uncover the contribution of individual actin regulators to the migration of immune cells in the context of their development and function.

Inborn errors of immunity manifesting as atopic disorders

Inborn errors of immunity are traditionally best known for enhancing susceptibility to infections. However, allergic inflammation, among other types of immune dysregulation, occurs frequently in patients with inborn errors of immunity. As such, the term primary atopic disorders (PADs) was recently coined to describe the group of heritable monogenic allergic disorders. It is becoming increasingly important for clinicians to recognize that allergic diseases such as food allergy, atopic dermatitis, and allergic asthma are expressions of misdirected immunity, and in patients who present with severe, early-onset, or coexisting allergic conditions, these can be indications of an underlying PAD. Identifying monogenic allergic disease through next-generation sequencing can dramatically improve outcomes by allowing the use of precision-based therapy targeting the patient's underlying molecular defect. It is therefore imperative that clinicians recognize PADs to be able to provide informed therapeutic options and improve patient outcomes. Here, we summarize the clinical features commonly seen with each of the currently known PADs, identify clinical warning signs that warrant assessment for PADs, and lastly, discuss the benefits of timely diagnosis and management of these conditions.

Common Variable Immunodeficiency and Other Immunodeficiency Syndromes in Bronchiectasis

Immunodeficiency represents a vast number of diseases and syndromes. Both primary and secondary forms of immunodeficiency are important contributors to the development of bronchiectasis. Primary immune deficiencies, in particular, are increasingly identified and defined as contributors. Specific immune deficiencies that are closely associated with bronchiectasis and as discussed in this article are common variable immunodeficiency, specific antibody deficiency, immunodeficiencies involving immunoglobulin E, DOCK8 immunodeficiency, phosphoglucomutase 3 deficiency, activated phosphoinositide 3-kinase delta syndrome, and X-linked agammaglobulinemia. Each of these primary immune deficiencies has unique nuances. Vigilance for these unique signs and symptoms is likely to improve recognition of specific immunodeficiency in the idiopathic bronchiectasis patient. Secondary forms of immunodeficiency occur as a result of a separate disease process. Graft versus host disease, malignancy, and human immunodeficiency virus are three classic examples discussed in this article. An awareness of the potential for these disease settings to lead to bronchiectasis is necessary to optimize patient care. With understanding and mindfulness toward the intricate relationship between bronchiectasis and immunodeficiency, there is an opportunity to elucidate pathophysiologic underpinnings between these two syndromes.

DOCK8 deficiency causes a skewing to type 2 immunity in the gut with expansion of group 2 innate lymphoid cells

Dedicator of cytokinesis 8 (DOCK8) is a guanine nucleotide exchange factor (GEF) for Cdc42. In humans, homozygous or compound heterozygous deletions in DOCK8 cause a combined immunodeficiency characterized by various allergic diseases including food allergies. Although group 2 innate lymphoid cells (ILC2s) contribute to the development of allergic inflammation by producing interleukin (IL)-5 and IL-13, the role of ILC2s in DOCK8 deficiency has not been fully explored. With the use of cytometry by time-of-flight (CyTOF), we performed high-dimensional phenotyping of intestinal immune cells and found that DOCK8-deficient (Dock8-/-) mice exhibited expansion of ILC2s and other leukocytes associated with type 2 immunity in the small intestine. Moreover, IL-5- and IL-13-producing cells markedly increased in Dock8-/- mice, and the majority of them were lineage-negative cells, most likely ILC2s. Intestinal ILC2s expanded when DOCK8 expression was selectively deleted in hematopoietic cells. Importantly, intestinal ILC2 expansion was also observed in Dock8VAGR mice having mutations in the catalytic center of DOCK8, thereby failing to activate Cdc42. Our findings indicate that DOCK8 is a negative regulator of intestinal ILC2s to inhibit their expansion via Cdc42 activation, and that deletion of DOCK8 causes a skewing to type 2 immunity in the gut.

Treatment options for DOCK8 deficiency-related severe dermatitis

BACKGROUND

Cutaneous manifestations of dedicator of cytokinesis 8 gene (DOCK8) deficiency, a combined type of T and B cell immunodeficiency, previously designated as autosomal recessive hyper IgE syndrome, includes dermatitis and skin infections. There are limited treatment options for dermatitis related to the syndrome.

OBJECTIVE

To describe a cohort of patients with DOCK8 deficiency with a focus on the treatment of their cutaneous manifestations.

METHODS

A retrospective study on all children with the genetic diagnosis of DOCK8 deficiency treated at the Sheba Medical Center between 1/1/2003 and 1/1/2021 was preformed. Collected data included: demographic features, family history, laboratory, genetic testing, skin manifestations, treatment, and disease course. Description of two cases of severe recalcitrant dermatitis treated with dupilumab is detailed.

RESULTS

Nine children with a genetic diagnosis of DOCK8 deficiency were included, of whom six were girls (66%) with a median age of 8.5 (±2.2 SD) years. The median age at diagnosis was 2.8 (±2.6 SD) years. Six patients were born to consanguineous parents. Five out of six patients who received hematopoietic stem cell transplantation (HSCT) had a complete response, and one was recently transplanted. Of note, two patients, while awaiting HSCT, were treated with dupilumab for their severe dermatitis resulting in a marked improvement of the cutaneous manifestations and pruritus.

CONCLUSIONS

Hematopoietic stem cell transplantation is the gold standard and most effective therapy for patients with DOCK8 deficiency. Dupilumab, a biological therapy indicated for atopic dermatitis and other Th2 derived dermatoses, is an excellent option for dermatitis in patients with DOCK8 deficiency and can be used as a bridge before HSCT. Larger studies are needed to confirm this observation.

DOCK8-related Immunodeficiency Syndrome (DIDS): Report of Novel Mutations in Iranian Patients

DOCK8 immunodeficiency syndrome (DIDS) is a rare autosomal recessive (AR) disorder characterized by elevated serum IgE levels, eosinophilia, recurrent cutaneous infections, severe eczema, and sinopulmonary and gastrointestinal infections. This syndrome is a multisystem disease that is associated with both immune deficiency and neurological complications. In this study, we describe the clinical characteristics of two Iranian patients with DOCK8 deficiency and propose possible mechanisms for this condition. By using whole exome sequencing (WES), we identified two novel mutations, namely c.3233_3234del AG (p.Q1078fs) in exon 6 and a large deletion with 94 kb (c.405-3231 deletion, p.K135fs), in these two patients. These variations are confirmed with Sanger sequencing and CGH array. Subsequent co-segregation analysis is performed to identify inheritance patterns. Both patients were homozygote and their parents were heterozygote for the variations. For further investigation, prediction tools were applied to identify the pathogenicity of the variations and also for modeling the truncated proteins. The patients did not show neurological abnormalities associated with a deficiency of the N terminal region of DOCK8. The absence of neurological complications in the first patient is justifiable due to the maintenance of the proline-rich region in DOCK8, but for the second patient with expanded deletion which is almost like null DOCK8 protein, it is not presumable, pointing to the fact that the C terminal region of the protein might have functions in the proliferation and migration neurons in the peripheral nervous system. Alternatively, it is possible that neurological abnormalities follow an age-dependent pattern, leading to the appearance of related symptoms later in life. Further multiple functional studies are needed to model different identified variants in animal models to confirm our results and suggest possible mechanisms associated with DOCK8 deficiency in this study.

A conserved PI(4,5)P2-binding domain is critical for immune regulatory function of DOCK8

This study uncovers a critical role of DOCK8 in coupling PI(4,5)P2 signaling with Cdc42 activation through its DHR-1 domain during interstitial leukocyte migration.

DOCK8 is a Cdc42-specific guanine-nucleotide exchange factor that is essential for development and functions of various subsets of leukocytes in innate and acquired immune responses. Although DOCK8 plays a critical role in spatial control of Cdc42 activity during interstitial leukocyte migration, the mechanism remains unclear. We show that the DOCK homology region (DHR)-1 domain of DOCK8 binds specifically to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and is required for its recruitment to the plasma membrane. Structural and biochemical analyses reveal that DOCK8 DHR-1 domain consists of a C2 domain-like core with loops creating the upper surface pocket, where three basic residues are located for stereospecific recognition of phosphoinositides. Substitution of the two basic residues, K576 and R581, with alanine abolished PI(4,5)P2 binding in vitro, ablated the ability of DOCK8 to activate Cdc42 and support leukocyte migration in three-dimensional collagen gels. Dendritic cells carrying the mutation exhibited defective interstitial migration in vivo. Thus, our study uncovers a critical role of DOCK8 in coupling PI(4,5)P2 signaling with Cdc42 activation for immune regulation.

DOCK8 deficiency diminishes thymic T-regulatory cell development but not thymic deletion

Objective

To define the effect of DOCK8 deficiency on thymic tolerance in mice.

Methods

Thymocytes from wild‐type (Dock8^+/+) and DOCK8‐deficient (Dock8^pri/pri) mice were examined by flow cytometry. Some mice had transgenic expression of the BCL2 anti‐apoptotic protein in haemopoietic cells. Some mice expressed the transgenic 3A9 T‐cell receptor (TCR), which triggers thymocyte deletion in mice also expressing hen egg lysozyme under the insulin promoter.

Results

In Dock8^pr/pri mice, the proportion of thymocytes induced to acquire tolerance at the immature CCR7⁻ stage was normal. Deletion of strongly self‐reactive CD4⁺ thymocytes occurred efficiently in Dock8^pri/pri mice in a TCR‐transgenic model that requires self‐antigen transfer from epithelial cells to bone marrow (BM)‐derived antigen‐presenting cells. Thymic Foxp3⁺ T‐regulatory cells (T_REG) and Helios⁺ Foxp3⁻ T_REG precursors were decreased in Dock8^pri/pri mice, including when apoptosis was inhibited by BCL2 transgene expression. Dock8^pri/pri thymic T_REG expressed CD25 and CTLA‐4 at normal levels. The results suggest that DOCK8 deficiency does not affect the function of BM‐derived antigen‐presenting cells in the thymus, the TCR self‐reactivity threshold that activates tolerance mechanisms in thymocytes or the apoptotic deletion of these thymocytes. However, DOCK8 is required to prevent a subset of developing T_REG cells from undergoing cell death via a mechanism that is distinct from apoptosis.

Conclusion

DOCK8 deficiency diminishes T_REG development in the thymus without compromising thymocyte deletion.

Migration-induced cell shattering due to DOCK8 deficiency causes a type 2-biased helper T cell response

Mutations that impact immune cell migration and result in immune deficiency illustrate the importance of cell movement in host defense. In humans, loss-of-function mutations in DOCK8, a guanine exchange factor involved in hematopoietic cell migration, lead to immunodeficiency and, paradoxically, allergic disease. Here, we demonstrate that, like humans, Dock8-/- mice have a profound type 2 CD4+ helper T (TH2) cell bias upon pulmonary infection with Cryptococcus neoformans and other non-TH2 stimuli. We found that recruited Dock8-/-CX3CR1+ mononuclear phagocytes are exquisitely sensitive to migration-induced cell shattering, releasing interleukin (IL)-1β that drives granulocyte-macrophage colony-stimulating factor (GM-CSF) production by CD4+ T cells. Blocking IL-1β, GM-CSF or caspase activation eliminated the type-2 skew in mice lacking Dock8. Notably, treatment of infected wild-type mice with apoptotic cells significantly increased GM-CSF production and TH2 cell differentiation. This reveals an important role for cell death in driving type 2 signals during infection, which may have implications for understanding the etiology of type 2 CD4+ T cell responses in allergic disease.

Genetic susceptibility to fungal infection in children

PURPOSE OF REVIEW

Fungal infections have steadily increased in incidence, emerging as a significant cause of morbidity and mortality in patients with iatrogenic immunosuppression. Simultaneously, we have witnessed a growing population of newly described inherited immune disorders that have enhanced our understanding of the human immune response against fungi. In the present review, we provide an overview and diagnostic roadmap to inherited disorders which confer susceptibility to superficial and invasive fungal infections.

RECENT FINDINGS

Inborn errors of fungal immunity encompass a heterogeneous group of disorders, some of which confer fungal infection-specific susceptibility, whereas others also feature broader infection vulnerability and/or noninfectious manifestations. Infections by Candida, Aspergillus, endemic dimorphic fungi, Pneumocystis, and dermatophytes along with their organ-specific presentations provide clinicians with important clues in the assessment of patients with suspected immune defects.

SUMMARY

The absence of iatrogenic risk factors should raise suspicion for inborn errors of immunity in children and young adults with recurrent or severe fungal diseases. Expeditious diagnosis and prompt initiation of antifungal therapy and management of complications are paramount to achieve remission of fungal disease in the setting of primary immunodeficiency disorders.

The Child with Elevated IgE and Infection Susceptibility

PURPOSE OF REVIEW

Over the last 13 years, the genetic etiologies have been determined for multiple conditions causing elevated serum IgE, infection susceptibilities, and variable other features. In this review, we discuss the clinical presentation, laboratory features, and genetics of these diseases caused by mutations in STAT3, DOCK8, PGM3, IL6ST, ZNF341, IL6R, IL6ST, CARD11, and CARD14, with particular focus given to STAT3LOF and DOCK8 deficiency.

RECENT FINDINGS

Defining the phenotype of each of these syndromes with high IgE and infection susceptibility shows that some have a pronounced connective tissue phenotype such as STAT3LOF and IL6ST deficiency, some have worse viral susceptibility such as DOCK8 deficiency and heterozygous LOF CARD11, and some have more severe allergy and eczema such as LOF CARD14. Studying these distinct but overlapping monogenic diseases will allow a better understanding of more common disease processes such as allergy, eczema, infection susceptibility, scoliosis, and aneurysm.

Clinical, immunological features and follow up of 20 patients with dedicator of cytokinesis 8 (DOCK8) deficiency

Biallelic mutations in the dedicator of cytokinesis 8 gene (DOCK8) cause a progressive combined immunodeficiency (CID) characterized by susceptibility to severe viral skin infections, atopic diseases, recurrent respiratory infections, and malignancy. Hematopoietic stem cell transplantation (HSCT) is only curative treatment for the disease. However, there is limited information about long-term outcome of HSCT and its effect to protect against cancer development in DOCK8-deficient patients. In this study, we retrospectively evaluated clinical and immunologic characteristics of 20 DOCK8-deficient patients and outcome of 11 patients who underwent HSCT. We aimed to report the experience of our center and the result of the largest transplantation series of DOCK8 deficiency in our country. Median follow-up time is 71 months (min-max: 16-172) in all patients and 48 months (min-max: 5-84) in transplanted patients. Atopic dermatitis (18/20), recurrent respiratory tract infections (17/20), and food allergy (14/20) were the most frequent clinical manifestations. Failure to thrive (13/20), liver problems (12/20), bronchiectasis (11/20), chronic diarrhea (10/21), and autism spectrum disorders (3/20) were remarkable findings in our series. Elevated IgE level (20/20) and eosinophilia (17/20), low IgM level (15/20), and decreased CD3+ T (10/20) and CD4+ T (11/20) cell count were prominent laboratory findings. HSCT was performed in 11 patients. All patients achieved adequate engraftment and showed improvement in their clinical and immunologic findings. Atopic dermatitis and food allergies improved in all patients, and their dietary restriction was stopped except one patient who was transplanted recently. The frequency of infections was decreased. The overall survival is 91% in HSCT-received patients and 80% in all. HSCT at the earliest possible period with most suitable donor- and patient-specific appropriate conditioning regimen and GvHD prophylaxis is lifesaving for DOCK8 deficiency cases.

DOCK family proteins: key players in immune surveillance mechanisms

Dedicator of cytokinesis (DOCK) proteins constitute a family of evolutionarily conserved guanine nucleotide exchange factors (GEFs) for the Rho family of GTPases. Although DOCK family proteins do not contain the Dbl homology domain typically found in other GEFs, they mediate the GTP–GDP exchange reaction through the DOCK homology region-2 (DHR-2) domain. In mammals, this family consists of 11 members, each of which has unique functions depending on the expression pattern and the substrate specificity. For example, DOCK2 is a Rac activator critical for migration and activation of leukocytes, whereas DOCK8 is a Cdc42-specific GEF that regulates interstitial migration of dendritic cells. Identification of DOCK2 and DOCK8 as causative genes for severe combined immunodeficiency syndromes in humans has highlighted their roles in immune surveillance. In addition, the recent discovery of a naturally occurring DOCK2-inhibitory metabolite has uncovered an unexpected mechanism of tissue-specific immune evasion. On the other hand, GEF-independent functions have been shown for DOCK8 in antigen-induced IL-31 production in helper T cells. This review summarizes multifaced functions of DOCK family proteins in the immune system.

Genetics and Epigenetics of Atopic Dermatitis: An Updated Systematic Review

BACKGROUND

Atopic dermatitis is a common inflammatory skin disorder that affects up to 15-20% of the population and is characterized by recurrent eczematous lesions with intense itching. As a heterogeneous disease, multiple factors have been suggested to explain the nature of atopic dermatitis (AD), and its high prevalence makes it necessary to periodically compile and update the new information available. In this systematic review, the focus is set at the genetic and epigenetic studies carried out in the last years.

METHODS

A systematic literature review was conducted in three scientific publication databases (PubMed, Cochrane Library, and Scopus). The search was restricted to publications indexed from July 2016 to December 2019, and keywords related to atopic dermatitis genetics and epigenetics were used.

RESULTS

A total of 73 original papers met the inclusion criteria established, including 9 epigenetic studies. A total of 62 genes and 5 intergenic regions were described as associated with AD.

CONCLUSION

Filaggrin (FLG) polymorphisms are confirmed as key genetic determinants for AD development, but also epigenetic regulation and other genes with functions mainly related to the immune system and extracellular matrix, reinforcing the notion of skin homeostasis breakage in AD.

Genodermatoses with malignant potential

The hereditary nature of some forms of cancer was recognized long ago. Over time, recognition of associated findings led to the delineation of numerous hereditary cancer syndromes. Many of these syndromes also have cutaneous manifestations, the recognition of which can lead to their early identification. Recognition of these syndromes allows vigilant surveillance and preemptive treatment, which can dramatically impact the risks of morbidity and mortality for affected patients. The rise of rapid and accurate genetic testing now allows the early identification of asymptomatic at risk family members so that monitoring can be initiated as early as possible. The dermatologist plays a critical role in early identification of these syndromes and, in many cases, their treatment. This review summarizes many known hereditary cancer syndromes with cutaneous findings, their etiology, identification, evaluation, and management. Importantly, this is an ever evolving topic and new findings and syndromes will continue to be recognized. The dermatologist must be always alert to ensure they are detected.

Genetic susceptibility to EBV infection: insights from inborn errors of immunity

Epstein-Barr virus (EBV) is a ubiquitous human pathogen, infecting > 90% of the adult population. In the vast majority of healthy individuals, infection with EBV runs a relatively benign course. However, EBV is by no means a benign pathogen. Indeed, apart from being associated with at least seven different types of malignancies, EBV infection can cause severe and often fatal diseases-hemophagocytic lymphohistiocytosis, lymphoproliferative disease, B-cell lymphoma-in rare individuals with specific monogenic inborn errors of immunity. The discovery and detailed investigation of inborn errors of immunity characterized by heightened susceptibility to, or increased frequency of, EBV-induced disease have elegantly revealed cell types and signaling pathways that play critical and non-redundant roles in host-defense against EBV. These analyses have revealed not only mechanisms underlying EBV-induced disease in rare genetic conditions, but also identified molecules and pathways that could be targeted to treat severe EBV infection and pathological consequences in immunodeficient hosts, or even potentially enhance the efficacy of an EBV-specific vaccine.

Hyper IgE Syndrome Associated With Warts: A First Case of Dedicator of Cytokinesis 8 Deficiency in the Philippines

Hyper IgE syndrome (HIES) encompasses a group of primary immunodeficiency diseases (PIDs) that is characterized by severe atopy, and recurrent infections and markedly elevated serum IgE levels. The majority of HIES cases suffer from autosomal dominant mutations in the signal transducer and activator of transcription 3 gene. A minority of cases display autosomal recessive inheritance, and one form is caused by mutations in the dedicator of cytokinesis 8 (DOCK8) gene. Here we describe the first recognized and diagnosed case of DOCK8 deficiency in the Philippines. A 14 year-old-girl was referred due to recalcitrant atopic dermatitis, recurrent sinopulmonary infections, with widespread warts on the face, trunk and extremities. She had no coarse facial features or retained primary teeth, whereas she presented with widespread viral skin infections and multiple allergic diseases. Laboratory examinations revealed elevations in eosinophil count and serum IgE. The level of T-cell receptor excision circles was undetectable. The patient was suspected to have HIES with a probable DOCK8 deficiency. Genetic analysis disclosed a large genomic deletion involving exons 2-4 in the DOCK8 gene. A combination of recalcitrant atopic dermatitis, asthma, food allergies, with viral skin infections should increase the physician's consideration of a PID. Patients with HIES accompanied by warts and T-cell deficiency can be strongly suspected to have DOCK8 deficiency.

Allogeneic hematopoietic stem cell and liver transplantation in a young girl with dedicator of cytokinesis 8 protein deficiency

DOCK8 deficiency is a rare inherited combined immunodeficiency, caused by mutations in the DOCK8 gene. We describe a case with DOCK8 deficiency associated with severe CLD in whom orthotopic LT was performed successfully after allogeneic HSCT. A 5 year-old girl with DOCK8 deficiency presented with mild direct hyperbilirubinemia and abnormal GGT level and without a previous history of jaundice. She had severe growth retardation, hepatosplenomegaly and generalized eczema. Progressive worsening of CLD was observed within 4 months. Investigations for etiology of liver disease were negative. Liver biopsy showed bridging necrosis, cholestasis and, cirrhosis. Recurrent immune hemolytic crisis and several viral infections developed in follow-up. She underwent whole cadaveric LT for end-stage liver disease (ESLD) 1 year after allogenic HSCT from a full matched related donor. The postoperative course was uneventful. The patient is alive with normal liver function and moderate skin graft versus host disease for 36 months after LT. In conclusion DOCK8 deficiency can be associated with severe CLD. Successful LT following HSCT is possible in patients with ESLD in DOCK8 deficiency. The timing of LT is challenging in patients requiring both HSCT and LT since conditioning regimens for HSCT can be highly hepatotoxic and the patients with suboptimal liver function can become decompensated during HSCT.

Flow Cytometric-Based Analysis of Defects in Lymphocyte Differentiation and Function Due to Inborn Errors of Immunity

The advent of flow cytometry has revolutionized the way we approach our research and answer specific scientific questions. The flow cytometer has also become a mainstream diagnostic tool in most hospital and pathology laboratories around the world. In particular the application of flow cytometry has been instrumental to the diagnosis of primary immunodeficiencies (PIDs) that result from monogenic mutations in key genes of the hematopoietic, and occasionally non-hematopoietic, systems. The far-reaching applicability of flow cytometry is in part due to the remarkable sensitivity, down to the single-cell level, of flow-based assays and the extremely user-friendly platforms that enable comprehensive analysis, data interpretation, and importantly, robust and rapid methods for diagnosing PIDs. A prime example is the absence of peripheral blood B cells in patients with agammaglobulinemia due to mutations in BTK or related genes in the BCR signaling pathway. Similarly, the development of intracellular staining protocols to detect expression of SAP, XIAP, or DOCK8 expedites the rapid diagnosis of the X-linked lymphoproliferative diseases or an autosomal recessive form of hyper-IgE syndrome (HIES), respectively. It has also become evident that distinct cohorts of PID patients exhibit unique “lymphocyte phenotypic signatures” that are often diagnostic even prior to identifying the genetic lesion. Flow cytometry-based sorting provides a technique for separating specific subsets of immune cells such that they can be studied in isolation. Thus, flow-based assays can be utilized to measure immune cell function in patients with PIDs, such as degranulation by cytotoxic cells, cytokine expression by many immune cells (i.e., CD4⁺ and CD8⁺ T cells, macrophages etc.), B-cell differentiation, and phagocyte respiratory burst in vitro. These assays can also be performed using unfractionated PBMCs, provided the caveat that the composition of lymphocytes between healthy donors and the PID patients under investigation is recognized. These functional deficits can assist not only in the clinical diagnosis of PIDs, but also reveal mechanisms of disease pathogenesis. As we move into the next generation of multiparameter flow cytometers, here we review some of our experiences in the use of flow cytometry in the study, diagnosis, and unraveling the pathophysiology of PIDs.

Identification of a T follicular helper cell subset that drives anaphylactic IgE

Cross-linking of high-affinity immunoglobulin E (IgE) results in the life-threatening allergic reaction anaphylaxis. Yet the cellular mechanisms that induce B cells to produce IgE in response to allergens remain poorly understood. T follicular helper (T_FH) cells direct the affinity and isotype of antibodies produced by B cells. Although T_FH cell-derived interleukin-4 (IL-4) is necessary for IgE production, it is not sufficient. We report a rare population of IL-13-producing T_FH cells present in mice and humans with IgE to allergens, but not when allergen-specific IgE was absent or only low-affinity. These "T_FH13" cells have an unusual cytokine profile (IL-13^hiIL-4^hiIL-5^hiIL-21^lo) and coexpress the transcription factors BCL6 and GATA3. T_FH13 cells are required for production of high- but not low-affinity IgE and subsequent allergen-induced anaphylaxis. Blocking T_FH13 cells may represent an alternative therapeutic target to ameliorate anaphylaxis.

Gene-environment interactions in primary atopic disorders

Environmental factors modify disease presentation and severity in allergic disorders. Primary atopic disorders (PADs) are a heterogenous group of single gene disorders that lead to significant atopic and allergic disease manifestations. However, a number of these monogenic diseases have variable penetrance suggesting that gene-gene and/or gene-environment interactions could modulate the clinical phenotype. Environmental factors such as diet, the microbiome at the epithelial-environment interface, the presence and/or extent of infection, and psychologic stress can alter disease phenotypic expression of allergic diseases, and PADs provide discrete contexts in which to understand these influences. We outline how gene-environment interactions likely contribute to a variable penetrance and expressivity in PADs. Dietary modifications of both macronutrients and/or micronutrients alter T-cell metabolism and may influence effector T-cell function. The mucosal microbiome may affect local inflammation and may remotely influence regulatory elements, while psychologic stress can affect mast cell and other allergic effector cell function. Understanding gene-environment interactions in PADs can hopefully provide a foundation for interrogating gene-environment interactions to common allergic disorders, and also present opportunities for personalized interventions based on the altered pathways and environmental influences in affected individuals.