DOCK8 enforces immunological tolerance by promoting IL-2 signaling and immune synapse formation in Tregs

Regulatory T-cell dysfunction and cutaneous exposure to Staphylococcus aureus underlie eczema in DOCK8 deficiency

BACKGROUND

Dedicator of cytokinesis 8 (DOCK8)-deficient patients have severe eczema, elevated IgE, and eosinophilia, features of atopic dermatitis (AD).

OBJECTIVE

We sought to understand the mechanisms of eczema in DOCK8 deficiency.

METHODS

Skin biopsy samples were characterized by histology, immunofluorescence microscopy, and gene expression. Skin barrier function was measured by transepidermal water loss. Allergic skin inflammation was elicited in mice by epicutaneous sensitization with ovalbumin (OVA) or cutaneous application of Staphylococcus aureus.

RESULTS

Skin lesions of DOCK8-deficient patients exhibited type 2 inflammation, and the patients' skin was colonized by Saureus, as in AD. Unlike in AD, DOCK8-deficient patients had a reduced FOXP3:CD4 ratio in their skin lesions, and their skin barrier function was intrinsically intact. Dock8-/- mice exhibited reduced numbers of cutaneous T regulatory (Treg) cells and a normal skin barrier. Dock8-/- and mice with an inducible Dock8 deletion in Treg cells exhibited increased allergic skin inflammation after epicutaneous sensitization with OVA. DOCK8 was shown to be important for Treg cell stability at sites of allergic inflammation and for the generation, survival, and suppressive activity of inducible Treg cells. Adoptive transfer of wild-type, but not DOCK8-deficient, OVA-specific, inducible Treg cells suppressed allergic inflammation in OVA-sensitized skin of Dock8-/- mice. These mice developed severe allergic skin inflammation and elevated serum IgE levels after topical exposure to Saureus. Both were attenuated after adoptive transfer of WT but not DOCK8-deficient Treg cells.

CONCLUSION

Treg cell dysfunction increases susceptibility to allergic skin inflammation in DOCK8 deficiency and synergizes with cutaneous exposure to Saureus to drive eczema in DOCK8 deficiency.

Metabolic fitness of IgA+ plasma cells in the gut requires DOCK8

Dedicator of cytokinesis 8 (DOCK8) mutations lead to a primary immunodeficiency associated with recurrent gastrointestinal infections and poor antibody responses but, paradoxically, heightened IgE to food antigens, suggesting that DOCK8 is central to immune homeostasis in the gut. Using Dock8-deficient mice, we found that DOCK8 was necessary for mucosal IgA production to multiple T cell-dependent antigens, including peanut and cholera toxin. Yet DOCK8 was not necessary in T cells for this phenotype. Instead, B cell-intrinsic DOCK8 was required for maintenance of antigen-specific IgA-secreting plasma cells (PCs) in the gut lamina propria. Unexpectedly, DOCK8 was not required for early B cell activation, migration, or IgA class switching. An unbiased interactome screen revealed novel protein partners involved in metabolism and apoptosis. Dock8-deficient IgA+ B cells had impaired cellular respiration and failed to engage glycolysis appropriately. These results demonstrate that maintenance of the IgA+ PC compartment requires DOCK8 and suggest that gut IgA+ PCs have unique metabolic requirements for long-term survival in the lamina propria.

Expanding IPEX: Inborn Errors of Regulatory T Cells

Regulatory T cells (Tregs) are critical for enforcing peripheral tolerance. Monogenic "Tregopathies" affecting Treg development, stability, and/or function commonly present with polyautoimmunity, atopic disease, and infection. While autoimmune manifestations may present in early childhood, as more disorders are characterized, conditions with later onset have been identified. Treg numbers in the blood may be decreased in Tregopathies, but this is not always the case, and genetic testing should be pursued when there is high clinical suspicion. Currently, hematopoietic cell transplantation is the only curative treatment, but gene therapies are in development, and small molecule inhibitors/biologics may also be used.

Insights into the pathogenesis of allergic disease from dedicator of cytokinesis 8 deficiency

Clinical observations and mechanistic studies in dedicator of cytokinesis 8 (DOCK8)-deficient patients and mice have revealed multiple mechanisms that could contribute to their unusually prevalent and severe allergic disease manifestations. Physical interactions of DOCK8 with STAT3 in B cells and T cells may contribute to increased IgE isotype switching or defective immune synapse formation that decreases T-cell receptor signal strength. A newly discovered TFH13 cell type promotes the development of life-threatening allergy via production of IL-13 and is increased in DOCK8 deficiency. Cytoskeletal derangements and cytothripsis, which were previously shown to account for the increased susceptibility to viral skin infection in DOCK8 deficiency, can lead to interplay between myeloid cells and T cells to ultimately increase production of IL-4, IL-5, and IL-13. Finally, the effects on type-2 innate lymphoid cells may also contribute to allergic disease.

Deciphering the role of DOCK8 in tumorigenesis by regulating immunity and the application of nanotechnology in DOCK8 deficiency therapy

The dedicator of cytokinesis 8 (DOCK8) immunodeficiency syndrome is a severe immune disorder and characterized by serum IgE levels elevation, fungal and viral infections, dermatitis and food allergies. It was well known that DOCK8 is crucial for the survival and function of multiple immune related cells. However, the critical role of DOCK8 on tumorigenesis through regulating immunity is poorly investigated. Accumulating evidences indicated that DOCK8 could affect tumorigenesis by regulating the immunity through immune cells, including NK cells, T cells, B cells and dendritic cells. Here, we summarized and discussed the critical role of DOCK8 in cytoskeleton reconstruction, CD4+ T cell differentiation, immune synaptic formation, tumor immune infiltration, tumor immune surveillance and tumorigenesis. Furthermore, the potential roles of nanotechnology in improving the hematopoietic stem cell transplantation-based therapy for DOCK8 deficiency diseases are also highlighted and discussed.

Retinoic acid signaling acts as a rheostat to balance Treg function

Regulatory T cells (Tregs) promote immune homeostasis by maintaining self-tolerance and regulating inflammatory responses. Under certain inflammatory conditions, Tregs can lose their lineage stability and function. Previous studies have reported that ex vivo exposure to retinoic acid (RA) enhances Treg function and stability. However, it is unknown how RA receptor signaling in Tregs influences these processes in vivo. Herein, we employed mouse models in which RA signaling is silenced by the expression of the dominant negative receptor (DN) RARα in all T cells. Despite the fact that DNRARα conventional T cells are hypofunctional, Tregs had increased CD25 expression, STAT5 pathway activation, mTORC1 signaling and supersuppressor function. Furthermore, DNRARα Tregs had increased inhibitory molecule expression, amino acid transporter expression, and metabolic fitness and decreased antiapoptotic proteins. Supersuppressor function was observed when wild-type mice were treated with a pharmacologic pan-RAR antagonist. Unexpectedly, Treg-specific expression of DNRARα resulted in distinct phenotypes, such that a single allele of DNRARα in Tregs heightened their suppressive function, and biallelic expression led to loss of suppression and autoimmunity. The loss of Treg function was not cell intrinsic, as Tregs that developed in a noninflammatory milieu in chimeric mice reconstituted with DNRARα and wild-type bone marrow maintained the enhanced suppressive capacity. Fate mapping suggested that maintaining Treg stability in an inflammatory milieu requires RA signaling. Our findings indicate that RA signaling acts as a rheostat to balance Treg function in inflammatory and noninflammatory conditions in a dose-dependent manner.

Inborn Errors of the Immune System Associated With Atopy

Atopic disorders, including atopic dermatitis, food and environmental allergies, and asthma, are increasingly prevalent diseases. Atopic disorders are often associated with eosinophilia, driven by T helper type 2 (Th2) immune responses, and triggered by disrupted barrier function leading to abnormal immune priming in a susceptible host. Immune deficiencies, in contrast, occur with a significantly lower incidence, but are associated with greater morbidity and mortality. A subset of atopic disorders with eosinophilia and elevated IgE are associated with monogenic inborn errors of immunity (IEI). In this review, we discuss current knowledge of IEI that are associated with atopy and the lessons these immunologic disorders provide regarding the fundamental mechanisms that regulate type 2 immunity in humans. We also discuss further mechanistic insights provided by animal models.

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.

Cutting Edge: DOCK8 Regulates a Subset of Dendritic Cells That Is Critical for the Development of Experimental Autoimmune Encephalomyelitis

Dedicator of cytokinesis 8 (DOCK8) is a guanine nucleotide exchange factor with an essential role in cytoskeletal rearrangement, cell migration, and survival of various immune cells. Interestingly, DOCK8-deficient mice are resistant to the development of experimental autoimmune encephalomyelitis (EAE). To understand if EAE resistance in these mice results from an alteration in dendritic cell (DC) functions, we generated mice with conditional deletion of DOCK8 in DCs and observed attenuated EAE in these mice compared with control mice. Additionally, we demonstrated that DOCK8 is important for the existence of splenic conventional DC2 and lymph node migratory DCs and further established that migratory DC, rather than resident DC, are essential for the generation and proliferation of pathogenic T cell populations upon immunization with myelin Ag in adjuvant. Therefore, our data suggest that limiting migratory DCs through DOCK8 deletion and possibly other mechanisms could limit the development of CNS autoimmunity.

DOCK8 Serves as a Prognostic Biomarker and Is Related to Immune Infiltration in Patients With HPV Positive Head and Neck Squamous Cell Carcinoma

Purpose:

Dedicator of cytokinesis 8 (DOCK8) was reported to have a vital link to immunoregulation. However, the mechanisms by which it drives immune infiltration in cancer remain uncertain. We tried to assess the role of DOCK8 in patients with cancer, especially human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC).

Methods:

Data on the expression and survival of DOCK8 in patients with various cancers were analyzed using the Oncomine and TIMER databases. The TIMER database assessed the relationship of DOCK8 with immune infiltration levels and various markers of multiple immune cells. Gene set enrichment analysis revealed tumor-associated biological processes related to DOCK8. ENCODE database was used to explore relevant transcription factors of DOCK8, and a PPI network was constructed using GENEMINIA. The expression and survival role of DOCK8 was confirmed in patients from independent GEO datasets.

Results:

We determined that DOCK8 expression was upregulated or downregulated in various cancers unlike in healthy tissues. A high expression of DOCK8 was significantly correlated with a favorable prognosis in HPV-positive HNSCC and lung adenocarcinoma (LUAD). Furthermore, multivariate Cox regression analysis revealed that DOCK8 was an independent prognostic factor of HPV-positive HNSCC. Additionally, elevated DOCK8 expression was positively correlated with multiple immune cell infiltration levels and immune marker expression associated with particular immune cell subsets. Also, 14 pathways involved in immune activities and carcinogenesis, 22 potential TFs, and co-expression proteins of DOCK8 indicated DOCK8 to be related to tumor-associated biological processes. Ultimately, we verified that DOCK8 is upregulated and confers a favorable overall survival and progression-free survival status in patients with HPV-positive HNSCC.

Conclusion:

These results elucidate that high expression of DOCK8 indicates a favorable prognosis in patients with HPV-positive HNSCC as well as increased microenvironmental immune infiltration levels. It would provide new insights into the prognosis predicting and clinical regimen decision making in patients with HPV-positive HNSCC.

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.

Case Report: Hypomorphic Function and Somatic Reversion in DOCK8 Deficiency in One Patient With Two Novel Variants and Sclerosing Cholangitis

DOCK8 deficiency is a combined immunodeficiency due to biallelic variants in dedicator of cytokinesis 8 (DOCK8) gene. The disease has a wide clinical spectrum encompassing recurrent infections (candidiasis, viral and bacterial infections), virally driven malignancies and immune dysregulatory features, including autoimmune (cytopenia and vasculitis) as well as allergic disorders (eczema, asthma, and food allergy). Hypomorphic function and somatic reversion of DOCK8 has been reported to result in incomplete phenotype without IgE overproduction. Here we describe a case of DOCK8 deficiency in a 8-year-old Caucasian girl. The patient's disease was initially classified as autoimmune thrombocytopenia, which then evolved toward a combined immunodeficiency phenotype with recurrent infections, persistent EBV infection and lymphoproliferation. Two novel variants (one deletion and one premature stop codon) were characterized, resulting in markedly reduced, but not absent, DOCK8 expression. Somatic reversion of the DOCK8 deletion was identified in T cells. Hypomorphic function and somatic reversion were associated with restricted T cell repertoire, decreased STAT5 phosphorylation and impaired immune synapse functioning in T cells. Although the patient presented with incomplete phenotype (absence of markedly increase IgE and eosinophil count), sclerosing cholangitis was incidentally detected, thus indicating that hypomorphic function and somatic reversion of DOCK8 may delay disease progression but do not necessarily prevent from severe complications.

DOCK8 Expression in Regulatory T Cells Maintains their Stability and Limits Contact Hypersensitivity

Chronic dermatitis is a hallmark of Dedicator of cytokinesis 8 (DOCK8) deficiency. The migration of DOCK8-deficient T cells to the skin and their survival there have been reported to be defective. Surprisingly, we found that Dock8^-/- mice demonstrated an exaggerated contact hypersensitivity (CHS) response to oxazolone with increased ear swelling, T-cell infiltration, and expression of Ifng. To understand the mechanisms of persistent skin inflammation in DOCK8 deficiency, we examined mice with selective deficiency of DOCK8 in T cells or T regulatory cells (Tregs) and found that both have exaggerated CHS. Moreover, oral tolerance to oxazolone, mediated by Tregs, was impaired in Dock8^-/- mice. Transfer of Tregs from oxazolone-sensitized wild-type mice, but not Dock8^-/- mice, reduced the CHS response of Dock8^-/- recipients. Lack of DOCK8 in Tregs resulted in their acquisition of a pathogenic FOXP3⁺T-bet⁺IFNγ⁺ phenotype at CHS sites and promoted their conversion into ex-Tregs. The transfer of Tregs from Dock8^-/- mice increased the CHS response of wild-type recipients to oxazolone. Thus, DOCK8 expression in Tregs limits CHS by promoting Treg stability and fitness in inflamed skin. Interventions aimed at ameliorating Treg function may be useful in treating skin inflammation in DOCK8 deficiency.

Transcriptional regulation of Treg homeostasis and functional specification

CD4+Foxp3+ regulatory T (Treg) cells are key players in keeping excessive inflammation in check. Mounting evidence has shown that Treg cells exert much more diverse functions in both immunological and non-immunological processes. The development, maintenance and functional specification of Treg cells are regulated by multilayered factors, including antigens and TCR signaling, cytokines, epigenetic modifiers and transcription factors (TFs). In the review, we will focus on TFs by summarizing their unique and redundant roles in Treg cells under physiological and pathophysiological conditions. We will also discuss the recent advances of Treg trajectories between lymphoid organs and non-lymphoid tissues. This review will provide an updated view of the newly identified TFs and new functions of known TFs in Treg biology.

DOCK8 is essential for LFA-1-dependent positioning of T follicular helper cells in germinal centers

T follicular helper (Tfh) cell migration into germinal centers (GCs) is essential for the generation of GC B cells and antibody responses to T cell-dependent (TD) antigens. This process requires interactions between lymphocyte function-associated antigen 1 (LFA-1) on Tfh cells and ICAMs on B cells. The mechanisms underlying defective antibody responses to TD antigens in DOCK8 deficiency are incompletely understood. We show that mice selectively lacking DOCK8 in T cells had impaired IgG antibody responses to TD antigens, decreased GC size, and reduced numbers of GC B cells. However, they developed normal numbers of Tfh cells with intact capacity for driving B cell differentiation into a GC phenotype in vitro. Notably, migration of DOCK8-deficient T cells into GCs was defective. Following T cell receptor (TCR)/CD3 ligation, DOCK8-deficient T cells had impaired LFA-1 activation and reduced binding to ICAM-1. Our results therefore indicate that DOCK8 is important for LFA-1-dependent positioning of Tfh cells in GCs, and thereby the generation of GC B cells and IgG antibody responses to TD antigen.

The regulation of DOCK family proteins on T and B cells

The dedicator of cytokinesis (DOCK) family proteins consist of 11 members, each of which contains 2 domains, DOCK homology region (DHR)-1 and DHR-2, and as guanine nucleotide exchange factors, they mediate activation of small GTPases. Both DOCK2 and DOCK8 deficiencies in humans can cause severe combined immunodeficiency, but they have different characteristics. DOCK8 defect mainly causes high IgE, allergic disease, refractory skin virus infection, and increased incidence of malignant tumor, whereas DOCK2 defect mainly causes early-onset, invasive infection with less atopy and increased IgE. However, the underlying molecular mechanisms causing the disease remain unclear. This paper discusses the role of DOCK family proteins in regulating B and T cells, including development, survival, migration, activation, immune tolerance, and immune functions. Moreover, related signal pathways or molecule mechanisms are also described in this review. A greater understanding of DOCK family proteins and their regulation of lymphocyte functions may facilitate the development of new therapeutics for immunodeficient patients and improve their prognosis.

CCL11 increases the proportion of CD4+CD25+Foxp3+ Treg cells and the production of IL‑2 and TGF‑β by CD4+ T cells via the STAT5 signaling pathway

CD4⁺ regulatory T (Treg) cells are associated with immune tolerance and antitumor immunosuppression. The aim of the present study was to investigate the role and molecular mechanism of C-C motif chemokine ligand 11 (CCL11) in the regulation of Treg cells from patients with breast cancer (BC) and healthy individuals in vitro, and from tumor-bearing mice in vivo. CD4⁺ T cells isolated from patients with BC or healthy individuals were incubated with anti-CCL11 neutralizing antibodies or recombinant human CCL11 protein, in the presence or absence of a STAT5 inhibitor. The serum CCL11 level and proportion of Treg cells characterized as CD4⁺CD25⁺forkhead box P3⁺ (Foxp3) among the CD4⁺ T cells in patients with BC and healthy individuals were analyzed by ELISA and flow cytometry, respectively. CCL11, C-C motif chemokine receptor 3 (CCR3), Foxp3, phosphorylated-STAT5 and STAT5 expression levels were determined by western blotting. The serum CCL11 level and the proportion of CD4⁺CD25⁺Foxp3⁺ Treg cells were significantly increased in patients with BC compared with healthy individuals. CCL11 blockade reduced the proportion of CD4⁺CD25⁺Foxp3⁺ Treg cells, the expression of CCR3 and Foxp3, and the level of STAT5 activation in tumor-associated CD4⁺ T cells, in a dose-dependent manner. CCL11 blockade also reduced the proportion of CD4⁺CD25⁺Foxp3⁺ Treg cells and the serum levels of interleukin (IL)-2 and transforming growth factor (TGF)-β1 in tumor-bearing mice. The recombinant human CCL11 protein increased the proportion of CD4⁺CD25⁺Foxp3⁺ Treg cells, the expression of CCR3 and Foxp3, and the release of IL-2 and TGF-β1 in non-tumor-associated CD4⁺ T cells via the STAT5 signaling pathway. The results of the present study may aid in identifying therapeutics that could further modulate the immune system during BC.

ILC3 deficiency and generalized ILC abnormalities in DOCK8-deficient patients

BACKGROUND

Dedicator of cytokinesis 8 (DOCK8) deficiency is the main cause of the autosomal recessive hyper-IgE syndrome (HIES). We previously reported the selective loss of group 3 innate lymphoid cell (ILC) number and function in a Dock8-deficient mouse model. In this study, we sought to test whether DOCK8 is required for the function and maintenance of ILC subsets in humans.

METHODS

Peripheral blood ILC1-3 subsets of 16 DOCK8-deficient patients recruited at the pretransplant stage, and seven patients with autosomal dominant (AD) HIES due to STAT3 mutations, were compared with those of healthy controls or post-transplant DOCK8-deficient patients (n = 12) by flow cytometry and real-time qPCR. Sorted total ILCs from DOCK8- or STAT3-mutant patients and healthy controls were assayed for survival, apoptosis, proliferation, and activation by IL-7, IL-23, and IL-12 by cell culture, flow cytometry, and phospho-flow assays.

RESULTS

DOCK8-deficient but not STAT3-mutant patients exhibited a profound depletion of ILC3s, and to a lesser extent ILC2s, in their peripheral blood. DOCK8-deficient ILC1-3 subsets had defective proliferation, expressed lower levels of IL-7R, responded less to IL-7, IL-12, or IL-23 cytokines, and were more prone to apoptosis compared with those of healthy controls.

CONCLUSION

DOCK8 regulates human ILC3 expansion and survival, and more globally ILC cytokine signaling and proliferation. DOCK8 deficiency leads to loss of ILC3 from peripheral blood. ILC3 deficiency may contribute to the susceptibility of DOCK8-deficient patients to infections.

Primary immunodeficiencies caused by mutations in actin regulatory proteins

The identification of patients with monogenic gene defects have illuminated the function of different proteins in the immune system, including proteins that regulate the actin cytoskeleton. Many of these actin regulatory proteins are exclusively expressed in leukocytes and regulate the formation and branching of actin filaments. Their absence or abnormal function leads to defects in immune cell shape, cellular projections, migration, and signaling. Through the study of patients' mutations and generation of mouse models that recapitulate the patients' phenotypes, our laboratory and others have gained a better understanding of the role these proteins play in cell biology and the underlying pathogenesis of immunodeficiencies and immune dysregulatory syndromes.

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

DOCK8 immunodeficiency syndrome (DIDS) is a progressive combined immunodeficiency that can be distinguished from other combined immunodeficiencies or hyperimmunoglobulinemia E syndromes in featuring (a) profound susceptibility to virus infections of the skin, with associated skin cancers, and (b) severe food allergies. The DOCK8 locus has many repetitive sequence elements that predispose to the generation of large germline deletions as well as recombination-mediated somatic DNA repair. Residual DOCK8 protein contributes to the variable disease phenotype. The severe virus infections of the skin, and probably also VZV-associated vasculopathy, reflect an important function of DOCK8, which is normally required to maintain lymphocyte shape integrity as the cells migrate through dense tissues. Loss of DOCK8 also causes immune deficits through other mechanisms including a milder generalized cell survival defect and skewing of T helper cell subsets. Recent work has uncovered the roles for DOCK8 in dendritic cell responses that can also help explain the virus susceptibility, as well as in regulatory T cells that might help explain autoimmunity in a minority of patients. Fortunately, hematopoietic stem cell transplantation cures the eczema and infection susceptibility of DIDS, but not necessarily the other disease manifestations including food allergies.

Interaction of septin 7 and DOCK8 in equine lymphocytes reveals novel insights into signaling pathways associated with autoimmunity

The GTP-binding protein septin 7 is involved in various cellular processes, including cytoskeleton organization, migration and the regulation of cell shape. Septin 7 function in lymphocytes, however, is poorly characterized. Since the intracellular signaling role of septin 7 is dependent on its interaction network, interaction proteomics was applied to attain novel knowledge about septin 7 function in hematopoietic cells. Our previous finding of decreased septin 7 expression in blood-derived lymphocytes in ERU, a spontaneous animal model for autoimmune uveitis in man, extended the role of septin 7 to a potential key player in autoimmunity. Here, we revealed novel insights into septin 7 function by identification of DOCK8 as an interaction partner in primary blood-derived lymphocytes. Since DOCK8 is associated with important immune functions, our finding of significantly decreased DOCK8 expression and altered DOCK8 interaction network in ERU might explain changes in immune response and shows the contribution of DOCK8 in pathomechanisms of spontaneous autoimmune diseases. Moreover, our analyses revealed insights in DOCK8 function, by identifying the signal transducer ILK as a DOCK8 interactor in lymphocytes. Our finding of the enhanced enrichment of ILK in ERU cases indicates a deviant influence of DOCK8 on inter- and intracellular signaling in autoimmune disease.

Human hyper-IgE syndrome: singular or plural?

Spectacular progress has been made in the characterization of human hyper-IgE syndrome (HIES) over the last 50 years. HIES is a primary immunodeficiency defined as an association of atopy in a context of very high serum IgE levels, characteristic bacterial and fungal diseases, low-level clinical and biological inflammation, and various non-hematopoietic developmental manifestations. Somewhat arbitrarily, three disorders were successively put forward as the underlying cause of HIES: autosomal dominant (AD) STAT3 deficiency, the only disorder corresponding to the original definition of HIES, and autosomal recessive (AR) DOCK8 and PGM3 deficiencies, in which atopy and high serum IgE levels occur in a context of manifestations not seen in patients with typical HIES. Indeed, these three disorders disrupt different molecular pathways, affect different cell types, and underlie different clinical phenotypes. Surprisingly, several other inherited inborn errors of immunity in which serum IgE levels are high, sometimes almost as high as those in HIES patients, are not considered to belong to the HIES group of diseases. Studies of HIES have been further complicated by the lack of a high serum IgE phenotype in all mouse models of the disease other than two Stat3 mutant strains. The study of infections in mutant mice has helped elucidate only some forms of HIES and infection. Mouse models of these conditions have also been used to study non-hematopoietic phenotypes for STAT3 deficiency, tissue-specific immunity for DOCK8 deficiency, and cell lineage maturation for PGM3 deficiency. We review here the history of the field of HIES since the first clinical description of this condition in 1966, together with the three disorders commonly referred to as HIES, focusing, in particular, on their mouse models. We propose the restriction of the term "HIES" to patients with an AD STAT3-deficiency phenotype, including the most recently described AR ZNF341 deficiency, thus excluding AR DOCK8 and PGM3 deficiencies from the definition of this disease.

Primary atopic disorders

Important insights from monogenic disorders into the immunopathogenesis of allergic diseases and reactions are discussed.

Monogenic disorders have provided fundamental insights into human immunity and the pathogenesis of allergic diseases. The pathways identified as critical in the development of atopy range from focal defects in immune cells and epithelial barrier function to global changes in metabolism. A major goal of studying heritable single-gene disorders that lead to severe clinical allergic diseases is to identify fundamental pathways leading to hypersensitivity that can be targeted to provide novel therapeutic strategies for patients with allergic diseases, syndromic and nonsyndromic alike. Here, we review known single-gene disorders leading to severe allergic phenotypes in humans, discuss how the revealed pathways fit within our current understanding of the atopic diathesis, and propose how some pathways might be targeted for therapeutic benefit.