B cells require DOCK8 to elicit and integrate T cell help when antigen is limiting
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ABSTRACT: Dedicator of cytokinesis 8 (DOCK8) immunodeficiency syndrome is characterized by a failure of the germinal center response, a process involving the proliferation and positive selection of antigen-specific B cells. While DOCK8-deficient B cells are recruited into germinal centers, we find that they are arrested at a light-zone stage. They are unable to respond to T cell–dependent survival and selection signals, and consequently differentiate into plasma cells or memory B cells. Although DOCK8-deficient B cells can acquire and present antigen to initiate activation of cognate T cells, integrin upregulation, B–T cell conjugate formation, and costimulation are insufficient for sustained activation of B and T cells when antigen availability is limited. Our findings provide an explanation for the failure of B cell-dependent humoral responses in DOCK8 immunodeficiency syndrome, and offer insights into how the level of available antigen modulates B–T cell interactions necessary for humoral immune responses and immune memory.
Project description:Retinoic-acid receptor-related orphan receptor-γt-positive (RORγt+) innate lymphoid cells (ILCs) produce interleukin (IL)-22 and IL-17, which are critical for protective immunity against enteric pathogens. The molecular mechanism underlying the development and survival of RORγt+ ILCs is not thoroughly understood. Here we show that Dedicator of cytokinesis 8 (DOCK8), a scaffolding protein involved in cytoskeletal rearrangement and cell migration, is essential for the protective immunity against Citrobacter rodentium. A comparative RNA sequencing-based analysis reveals an impaired induction of antimicrobial peptides in the colon of DOCK8-deficient mice, which correlates with high susceptibility to infection and a very low number of IL-22-producing RORγt+ ILCs in their GI tract. Furthermore, DOCK8-deficient RORγt+ ILCs are less responsive to IL-7 mediated signaling, more prone to apoptosis and produce less IL-22 due to a defect in IL-23-mediated STAT3 phosphorylation. Our studies reveal an unsuspected role of DOCK8 for the function, generation and survival of RORγt+ ILCs. Control and DOCK8 KO mice were infected with 2X109 CFU of Citrobacter rodentium and day 8 post infection mice were sacrificed and their colons were harvested (n=5) . Total RNA was purified from the infected colons with RNeasy mini kit (Qiagen). RNA sequencing was performed (pooled RNA sample from five mice in each group) at Genomic Core Facility Southwestern Medical Center, University of Texas.
Project description:T follicular helper (Tfh) cell migration into germinal centers (GC) is essential for the generation of GC B cells and antibody responses to T dependent (TD) antigens. This process requires interactions between 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 have impaired IgG antibody responses to TD antigens, decreased GC size, and reduced numbers of GC B cells. However, they develop 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 is defective. Following TCR/CD3 ligation, DOCK8 deficient T cells have impaired LFA-1 activation and reduced binding to ICAM-1. DOCK8 is important for LFA1-dependent positioning of Tfh cells in GCs, and thereby the generation of GC B cells and IgG antibody responses to TD antigen.
Project description:Mutations in the DOCK8 gene cause an autosomal recessive form of hyper-immunoglobulin E syndrome, characterised by chronic immunodeficiency with persistent microbial infection and increased incidence of malignancy. These manifestations suggest a defect in cytotoxic lymphocyte function and immune surveillance. However, how DOCK8 regulates NK cell-driven immune responses remains unclear. Here, we demonstrate that DOCK8 regulates NK cell cytotoxicity and cytokine production in response to target cell engagement or receptor ligation. Genetic ablation of DOCK8 in human NK cells attenuated cytokine transcription and secretion through inhibition of Src family kinase activation, particularly Lck, downstream of target cell engagement or NKp30 ligation. PMA/Ionomycin treatment of DOCK8 deficient NK cells rescued cytokine production, indicating a defect proximal to receptor ligation. Importantly, NK cells from DOCK8 deficient patients had attenuated production of IFNγ and TNFα upon NKp30 stimulation. Taken together, we reveal a novel molecular mechanism by which DOCK8 regulates NK cell driven immunity.
Project description:Retinoic-acid receptor-related orphan receptor-γt-positive (RORγt+) innate lymphoid cells (ILCs) produce interleukin (IL)-22 and IL-17, which are critical for protective immunity against enteric pathogens. The molecular mechanism underlying the development and survival of RORγt+ ILCs is not thoroughly understood. Here we show that Dedicator of cytokinesis 8 (DOCK8), a scaffolding protein involved in cytoskeletal rearrangement and cell migration, is essential for the protective immunity against Citrobacter rodentium. A comparative RNA sequencing-based analysis reveals an impaired induction of antimicrobial peptides in the colon of DOCK8-deficient mice, which correlates with high susceptibility to infection and a very low number of IL-22-producing RORγt+ ILCs in their GI tract. Furthermore, DOCK8-deficient RORγt+ ILCs are less responsive to IL-7 mediated signaling, more prone to apoptosis and produce less IL-22 due to a defect in IL-23-mediated STAT3 phosphorylation. Our studies reveal an unsuspected role of DOCK8 for the function, generation and survival of RORγt+ ILCs.
Project description:To examine the effect of DOCK8 deficiency on helper T cell differentiation, we employed microarray expression profiling and found that 850 genes were expressed at higher levels in Dock8–/– AND CD4+ T cells than Dock8+/– controls after antigen stimulation.
Project description:Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease of unknown cause. We show here that a novel T follicular helper cell type expressing the guanine nucleotide exchange factor DOCK8 on the cell surface causes SLE. These cells, which we have designated autoantibody-inducing CD4 T (aiCD4 T) cells, are generated after resuscitation from anergy following strong TCR stimulation by antigen. When mice normally not prone to autoimmune disease were repeatedly immunized with an antigen such as OVA, they generated DOCK8+ CD4 T cells. These DOCK8+ CD4 T cells, in vivo and also upon transfer to naïve mice, induced a variety of autoantibodies and lesions characteristic of SLE. TCR repertoire analyses showed that a substantial number of novel TCR repertoires were generated in the DOCK8+ CD4 T cells, which induced novel autoantibodies upon transfer to naïve mice. DOCK8+ CD4 T cells are localized in splenic red pulp, the space immunoreactive against a variety of antigens, and specifically increased in the peripheral blood of SLE patients in association with disease activity. Anti-DOCK8 antibody treatment ameliorated the lesions induced by DOCK8+ CD4 T cells and in lupus model (NZB x W) F1 mice. Thus, when CD4 T cells are overstimulated by an external disturbance, i.e., repeatedly stimulated with antigen, to levels that surpass the system’s self-organized criticality, these cells express DOCK8 on the cell surface and acquire autoreactivity via TCR re-revision at the periphery. These DOCK8+ CD4 T cells subsequently induce a variety of autoantibodies and SLE.
Project description:Analysis of DOCK8 deficient animals revealed a key role for this protein the survival and maintenance of natural killer T cells. This work lead to the identification of genes regulated by the guanine exchange factor, DOCK8. Total RNA was extracted from 3 biological replicates of thymic, DOCK8 deficient NKT cells and compared using an Illumina microarray to WT NKT cells.
Project description: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.
Project description:Background: DOCK8 deficiency is an autosomal recessive form of hyperimmunoglobulinemia E syndrome (HIES). Severe atopic dermatitis (AD) shares with DOCK8 deficiency some clinical symptoms, including eczema, eosinophilia, and increased serum IgE levels. The deficiency of DOCK8 protein is potentially a life-threatening autosomal recessive HIES and only curable with bone marrow transplantation. Despite identified metabolomics and cytokine biomarkers, novel proteomics biomarkers need to be identified, as the connecting networks are critical to our understanding of this disease. Hence we performed serum proteomics profiling using LC-MSE SynaptG2. Method: Label-free untargeted proteomics analysis was used to identify potentially reliable, sensitive, and specific protein biomarkers in serum collected from DOCK8 (n=10), AD (n=9) patients, which were compared to ctrls (n=5). Results: From a total of 275 quantifiable proteins, binary comparisons between AD vs. Ctrl, DOCK8 vs. Ctrl, and DOCK8 vs. AD revealed 109, 105 and 85 dysregulated proteins, respectively. 24 among 85 proteins were specific potential biomarkers among the DOCK8 and AD groups. The sensitivity and specificity of few proteins like Claspin, Immunoglobulin kappa and heavy, complement components as potential biomarkers to distinguish between DOCK8 and AD patients were evaluated using the receiver operating characteristic curve. DOCK8 deficiency and AD groups' profiling revealed a shared role of ERK1/2 among the commonly dysregulated proteins. Conclusion: In this study, we have identified potential proteomics biomarkers and profile to distinguish between DOCK8 and AD, with possible diagnostic and therapeutic applications to help create effective interventions for managing these diseases. Further studies to confirm these associations in prospective cohorts are warranted.
Project description:Patients deficient in the guanine nucleotide exchange factor DOCK8 have decreased numbers and impaired in vitro function of T regulatory (Treg) cells and make autoantibodies, but seldom develop autoimmunity. We show that similarly, Dock8-/- mice have decreased numbers and impaired in vitrofunction of Treg cells, but do not develop autoimmunity. In contrast, mice with selective DOCK8 deficiency in Treg cells develop lymphoproliferation, autoantibodies, and gastrointestinal inflammation, despite normal percentage and in vitro function of Treg cells, suggesting that deficient T effector cell function might protect DOCK8 deficient patients from autoimmunity. We demonstrate that DOCK8 associates with STAT5 and is important for IL-2 driven STAT5 phosphorylation in Treg cells. DOCK8 localizes within the lamellar actin ring of the Treg cell immune synapse (IS). Dock8-/- Treg cells have abnormal TCR-driven actin dynamics, decreased adhesiveness, altered gene expression profile, an unstable IS with decreased recruitment of signaling molecules, and impaired transendocytosis of the co-stimulatory molecule CD86. These data suggest that DOCK8 enforces immunological tolerance by promoting IL-2 signaling, TCR-driven actin dynamics, and the IS in Treg cells.