Background Dedicator of cytokinesis 8 (DOCK8) deficiency is typified by recurrent infections, increased serum IgE levels, eosinophilia, and a high incidence of allergic and autoimmune manifestations. ...Objective We sought to determine the role of DOCK8 in the establishment and maintenance of human B-cell tolerance. Methods Autoantibodies were measured in the plasma of DOCK8-deficient patients. The antibody-coding genes from new emigrant/transitional and mature naive B cells were cloned and assessed for their ability to bind self-antigens. Regulatory T (Treg) cells in the blood were analyzed by means of flow cytometry, and their function was tested by examining their capacity to inhibit the proliferation of CD4+ CD25− effector T cells. Results DOCK8-deficient patients had increased levels of autoantibodies in their plasma. We determined that central B-cell tolerance did not require DOCK8, as evidenced by the normally low frequency of polyreactive new emigrant/transitional B cells in DOCK8-deficient patients. In contrast, autoreactive B cells were enriched in the mature naive B-cell compartment, revealing a defective peripheral B-cell tolerance checkpoint. In addition, we found that Treg cells were decreased and exhibited impaired suppressive activity in DOCK8-deficient patients. Conclusions Our data support a critical role for DOCK8 in Treg cell homeostasis and function and the enforcement of peripheral B-cell tolerance.
Background Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbers of T and B lymphocytes but with deficient cellular and humoral immunity. Most cases are ...sporadic, but autosomal recessive inheritance has been described. In most cases, the cause of CID remains unknown. Objective We wanted to identify the genetic cause of CID in 2 siblings, the products of a first-cousin marriage, who experienced recurrent bacterial and candidal infections with bronchiectasis, growth delay, and early death. Methods We performed immunologic, genetic, and biochemical studies in the 2 siblings, their family members, and healthy controls. Reconstitution studies were performed with T cells from mucosa-associated lymphoid tissue lymphoma-translocation gene 1–deficient ( Malt1 −/− ) mice. Results The numbers of circulating T and B lymphocytes were normal, but T-cell proliferation to antigens and antibody responses to vaccination were severely impaired in both patients. Whole genome sequencing of 1 patient and her parents, followed by DNA sequencing of family members and healthy controls, showed the presence in both patients of a homozygous missense mutation in MALT1 that resulted in loss of protein expression. Analysis of T cells that were available on one of the patients showed severely impaired IκBα degradation and IL-2 production after activation, 2 events that depend on MALT1. In contrast to wild-type human MALT1, the patients' MALT1 mutant failed to correct defective nuclear factor-κB activation and IL-2 production in MALT1-deficient mouse T cells. Conclusions An autosomal recessive form of CID is associated with homozygous mutations in MALT1 . If future patients are found to be similarly affected, they should be considered as candidates for allogeneic hematopoietic cell transplantation.
Background Dedicator of cytokinesis 8 (DOCK8) mutations are responsible for a rare primary combined immunodeficiency syndrome associated with severe cutaneous viral infections, increased IgE levels, ...autoimmunity, and malignancy. Natural killer (NK) cells are essential for tumor surveillance and defense against virally infected cells. NK cell function relies on Wiskott-Aldrich syndrome protein for filamentous actin (F-actin) accumulation at the lytic NK cell immunologic synapse. DOCK8 activates cell division cycle 42, which, together with Wiskott-Aldrich syndrome protein, coordinates F-actin reorganization. Although abnormalities in T- and B-cell function have been described in DOCK8-deficient patients, the role of NK cells in this disease is unclear. Objectives We sought to understand the role of DOCK8 in NK cell function to determine whether NK cell abnormalities explain the pathogenesis of the clinical syndrome of DOCK8 deficiency. Methods A cohort of DOCK8-deficient patients was assembled, and patients' NK cells, as well as NK cell lines with stably reduced DOCK8 expression, were studied. NK cell cytotoxicity, F-actin content, and lytic immunologic synapse formation were measured. Results DOCK8-deficient patients' NK cells and DOCK8 knockdown cell lines all had decreased NK cell cytotoxicity, which could not be restored after IL-2 stimulation. Importantly, DOCK8 deficiency impaired F-actin accumulation at the lytic immunologic synapse without affecting overall NK cell F-actin content. Conclusions DOCK8 deficiency results in severely impaired NK cell function because of an inability to form a mature lytic immunologic synapse through targeted synaptic F-actin accumulation. This defect might underlie and explain important attributes of the DOCK8 deficiency clinical syndrome, including the unusual susceptibility to viral infection and malignancy.
Background Dedicator of cytokinesis 8 (DOCK8) deficiency can be cured by allogeneic hematopoietic stem cell transplantation (HSCT). Reports of outcomes are still limited. Objective We sought to ...analyze the results of HSCT in patients with DOCK8 deficiency and report whether approaches resulting in mixed chimerism result in clinically relevant immune reconstitution. Methods We performed a retrospective chart review of 11 patients with DOCK8 deficiency and measured DOCK8 expression and cytokine production. Results Of 11 patients, 7 received HSCT from related and 4 from unrelated donors; 9 patients received busulfan-based conditioning regimens. Survival was excellent (10 91% of 11 patients alive), including a patient who had undergone liver transplantation. Patients showed significant improvements in the frequency and severity of infections. Although eczema resolved in all, food allergies and high IgE levels persisted in some patients. Lymphopenia, eosinophilia, low numbers of naive CD8+ T cells and switched memory B cells, and TH 1/TH 2 cytokine imbalance improved in most patients. Although the 8 matched related or unrelated donor recipients had full donor chimerism, all 3 recipients of mismatched unrelated donor HSCT had high levels of donor T-cell chimerism and low B-cell and myeloid cell chimerism (0% to 46%). Almost all switched memory B cells were of donor origin. All patients, including those with mixed chimerism, mounted robust antibody responses to vaccination. Conclusion Allogeneic HSCT ameliorated the infectious and atopic symptoms of patients with DOCK8 deficiency. In patients with mixed chimerism, selective advantage for donor-derived T cells and switched memory B cells promoted restoration of cellular and humoral immunity and protection against opportunistic infection.
Background Staphylococcus aureus is an opportunistic pathogen that colonizes the skin of patients with atopic dermatitis (AD) and aggravates their disease. Neutrophils and the cytokines IL-17A and ...IL-17F, which drive the expression of the neutrophil-attracting chemokines, are important for the clearance of S aureus infection. The cytokine IL-22 is often coproduced by IL-17–secreting cells. The levels of IL-22 are elevated in AD skin lesions. Objective We sought to determine the role of IL-22 in the clearance of S aureus infection of mouse skin subjected to tape stripping, a surrogate for scratching, a cardinal feature of AD. Methods S aureus was applied to the tape-stripped skin of wild-type and Il22 −/− mice. Bacterial burden was evaluated by enumerating colony-forming units. Quantitative PCR and ELISA were performed to quantify Il22 mRNA and IL-22 protein in mouse and human skin. Flow cytometry was used to enumerate neutrophils in the skin. Results Scratching the skin of healthy adults and tape stripping of mouse skin induced local expression of Il22 mRNA and IL-22 protein. Induction of Il22 expression by tape stripping was dependent on IL-23 and γδ T cells. Clearance of S aureus from tape-stripped skin was significantly impaired in Il22 −/− mice. Neutrophil infiltration and upregulation of expression of genes encoding the antimicrobial peptides antigen-6/urokinase-type plasminogen activator receptor related protein-1 and β-DEFENSIN 14 and the chemokine (C-X-C motif) ligand following tape stripping were significantly impaired in Il22 −/− mice. Conclusions These findings show that IL-22 is important for limiting the growth of S aureus on mechanically injured skin and caution that IL-23 and IL-22 blockade in patients with AD may enhance susceptibility to staphylococcal skin infection.
There are more than 180 different genetic causes of primary immunodeficiencies identified to date. Approaches for identifying causative mutations can be broadly classified into 3 strategies: ...(1) educated guesses based on known signaling pathways essential for immune cell development and function, (2) similarity of clinical phenotypes to mouse models, and (3) unbiased genetic approaches. Next-generation DNA sequencing permits efficient sequencing of whole genomes or exomes but also requires strategies for filtering vast amounts of data. Recent studies have identified ways to solve difficult cases, such as diseases with autosomal dominant inheritance, incomplete penetrance, or mutations in noncoding regions. This review focuses on recently identified primary immunodeficiencies to illustrate the strategies, technologies, and potential pitfalls in finding novel causes of these diseases.
IgE antibodies play a central role in the pathogenesis of atopic diseases and in host immunity against parasitic infections. IgE has potent activities on mast cells and basophils. IgE class switching ...is a very tightly controlled process, and serum IgE levels are very low compared with other immunoglobulin isotypes. Transcription factors that activate or inhibit the IgE gene promoter, as well as TH 1 and TH 2 cytokines are important in the regulation of IgE levels. Hyper-IgE syndrome; Wiskott-Aldrich syndrome; immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX); Omenn syndrome; and atypical complete DiGeorge syndrome are primary immune deficiencies that are associated with elevated serum IgE levels. Increased IgE levels in IPEX, Wiskott-Aldrich syndrome and Omenn syndrome are likely related to increased TH 2 cytokine production caused by decreased a number or function of CD4+ CD25+ forkhead box protein P3+ regulatory T cells. The link between signal transducer and activator of transcription 3 mutations and elevated serum IgE levels in hyper-IgE syndrome is unclear. Insight into IgE regulation provided by the study of primary immune deficiencies with elevated IgE has important implications for allergic diseases.
Background Leucine-rich repeat containing 8A (LRRC8A) is an ubiquitously expressed transmembrane protein with 17 leucine-rich repeats (LRRs) at its C-terminal end and is an essential component of the ...volume-regulated anion channel (VRAC), which controls cellular volume. A heterozygous mutation in LRRC8A that truncates the 2 terminal LRRs was reported in a patient with agammaglobulinemia and absent B cells and was demonstrated to exert a dominant negative effect on T- and B-cell development in mice. Lrrc8a −/− mice have severely defective T-cell development and function. It is not known whether the T- and B-cell defects caused by LRRC8A deficiency are caused by loss of VRAC activity. Objective We sought to determine whether VRAC activity is required for normal T-cell development and function. Methods VRAC activity was examined by using patch-clamp analysis. Flow cytometry was used to examine T-cell development. T-cell proliferation, cytokine secretion, and antibody titers were measured by using standard techniques. Results We demonstrate that the spontaneous mouse mutant ébouriffé (ebo/ebo) harbors a homozygous 2-bp frameshift mutation in Lrrc8a that truncates the 15 terminal LRRs of LRRC8A. The Lrrc8a ebo mutation does not affect protein expression but drastically diminishes VRAC activity in T cells. ebo/ebo mice share features with Lrrc8a −/− mice that include curly hair, infertility, reduced longevity, and kidney abnormalities. However, in contrast to Lrrc8a −/− mice, ebo/ebo mice have normal T-cell development and function and intact antibody response to T-dependent antigen. Conclusion LRRC8A-dependent VRAC activity is dispensable for T-cell development and function.
Background A subset of atopic dermatitis is associated with increased susceptibility to eczema herpeticum (ADEH+). We previously reported that common single nucleotide polymorphisms (SNPs) in the ...IFN-γ (IFNG) and IFN-γ receptor 1 (IFNGR1) genes were associated with the ADEH+ phenotype. Objective We sought to interrogate the role of rare variants in interferon pathway genes for the risk of ADEH+. Methods We performed targeted sequencing of interferon pathway genes ( IFNG , IFNGR1 , IFNAR1 , and IL12RB1 ) in 228 European American patients with AD selected according to their eczema herpeticum status, and severity was measured by using the Eczema Area and Severity Index. Replication genotyping was performed in independent samples of 219 European American and 333 African American subjects. Functional investigation of loss-of-function variants was conducted by using site-directed mutagenesis. Results We identified 494 single nucleotide variants encompassing 105 kb of sequence, including 145 common, 349 (70.6%) rare (minor allele frequency <5%), and 86 (17.4%) novel variants, of which 2.8% were coding synonymous, 93.3% were noncoding (64.6% intronic), and 3.8% were missense. We identified 6 rare IFNGR1 missense variants, including 3 damaging variants (Val14Met V14M, Val61Ile, and Tyr397Cys Y397C) conferring a higher risk for ADEH+ ( P = .031). Variants V14M and Y397C were confirmed to be deleterious, leading to partial IFNGR1 deficiency. Seven common IFNGR1 SNPs, along with common protective haplotypes (2-7 SNPs), conferred a reduced risk of ADEH+ ( P = .015-.002 and P = .0015-.0004, respectively), and both SNP and haplotype associations were replicated in an independent African American sample ( P = .004-.0001 and P = .001-.0001, respectively). Conclusion Our results provide evidence that both genetic variants in the gene encoding IFNGR1 are implicated in susceptibility to the ADEH+ phenotype.
Background Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A deficiency causes T− B+ natural killer–positive severe combined immunodeficiency or T-cell ...lymphopenia with severe viral infections. However, because all known human mutations in CORO1A abrogate protein expression, the role of the protein's functional domains in host immunity is unknown. Objective We sought to identify the cause of the primary immunodeficiency in 2 young adult siblings with a history of disseminated varicella, cutaneous warts, and CD4+ T-cell lymphopenia. Methods We performed immunologic, genetic, and biochemical studies in the patients, family members, and healthy control subjects. Results Both patients had CD4+ T-cell lymphopenia and decreased lymphocyte proliferation to mitogens. IgG, IgM, IgA, and specific antibody responses were normal. Whole-genome sequencing identified a homozygous frameshift mutation in CORO1A disrupting the last 2 C-terminal domains by replacing 61 amino acids with a novel 91-amino-acid sequence. The CORO1AS401fs mutant was expressed in the patients' lymphocytes at a level comparable with that of wild-type CORO1A in normal lymphocytes but did not oligomerize and had impaired cytoskeletal association. CORO1AS401fs was associated with increased filamentous actin accumulation in T cells, severely defective thymic output, and impaired T-cell survival but normal calcium flux and cytotoxicity, demonstrating the importance of CORO1A oligomerization and subcellular localization in T-cell homeostasis. Conclusions We describe a truncating mutation in CORO1A that permits protein expression and survival into young adulthood. Our studies demonstrate the importance of intact CORO1A C-terminal domains in thymic egress and T-cell survival, as well as in defense against viral pathogens.
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