A DOCK8-WIP-WASp complex links T cell receptors to the actin cytoskeleton

Wiskott-Aldrich syndrome (WAS) is associated with mutations in the WAS protein (WASp), which plays a critical role in the initiation of T cell receptor–driven (TCR-driven) actin polymerization. The clinical phenotype of WAS includes susceptibility to infection, allergy, autoimmunity, and malignancy and overlaps with the symptoms of dedicator of cytokinesis 8 (DOCK8) deficiency, suggesting that the 2 syndromes share common pathogenic mechanisms. Here, we demonstrated that the WASp-interacting protein (WIP) bridges DOCK8 to WASp and actin in T cells. We determined that the guanine nucleotide exchange factor activity of DOCK8 is essential for the integrity of the subcortical actin cytoskeleton as well as for TCR-driven WASp activation, F-actin assembly, immune synapse formation, actin foci formation, mechanotransduction, T cell transendothelial migration, and homing to lymph nodes, all of which also depend on WASp. These results indicate that DOCK8 and WASp are in the same signaling pathway that links TCRs to the actin cytoskeleton in TCR-driven actin assembly. Further, they provide an explanation for similarities in the clinical phenotypes of WAS and DOCK8 deficiency.United States. Public Health Service (RO1AI114588)United States. Public Health Service (K08AI114968

Expansion of immunoglobulin-secreting cells and defects in B cell tolerance in Rag-dependent immunodeficiency

The contribution of B cells to the pathology of Omenn syndrome and leaky severe combined immunodeficiency (SCID) has not been previously investigated. We have studied a mut/mut mouse model of leaky SCID with a homozygous Rag1 S723C mutation that impairs, but does not abrogate, V(D)J recombination activity. In spite of a severe block at the pro–B cell stage and profound B cell lymphopenia, significant serum levels of immunoglobulin (Ig) G, IgM, IgA, and IgE and a high proportion of Ig-secreting cells were detected in mut/mut mice. Antibody responses to trinitrophenyl (TNP)-Ficoll and production of high-affinity antibodies to TNP–keyhole limpet hemocyanin were severely impaired, even after adoptive transfer of wild-type CD4+ T cells. Mut/mut mice produced high amounts of low-affinity self-reactive antibodies and showed significant lymphocytic infiltrates in peripheral tissues. Autoantibody production was associated with impaired receptor editing and increased serum B cell–activating factor (BAFF) concentrations. Autoantibodies and elevated BAFF levels were also identified in patients with Omenn syndrome and leaky SCID as a result of hypomorphic RAG mutations. These data indicate that the stochastic generation of an autoreactive B cell repertoire, which is associated with defects in central and peripheral checkpoints of B cell tolerance, is an important, previously unrecognized, aspect of immunodeficiencies associated with hypomorphic RAG mutations

Decreased somatic hypermutation induces an impaired peripheral B cell tolerance checkpoint

Patients with mutations in AICDA, which encodes activation-induced cytidine deaminase (AID), display an impaired peripheral B cell tolerance. AID mediates class-switch recombination (CSR) and somatic hypermutation (SHM) in B cells, but the mechanism by which AID prevents the accumulation of autoreactive B cells in blood is unclear. Here, we analyzed B cell tolerance in AID-deficient patients, patients with autosomal dominant AID mutations (AD-AID), asymptomatic AICDA heterozygotes (AID+/-), and patients with uracil N-glycosylase (UNG) deficiency, which impairs CSR but not SHM. The low frequency of autoreactive mature naive B cells in UNG-deficient patients resembled that of healthy subjects, revealing that impaired CSR does not interfere with the peripheral B cell tolerance checkpoint. In contrast, we observed decreased frequencies of SHM in memory B cells from AD-AID patients and AID+/- subjects, who were unable to prevent the accumulation of autoreactive mature naive B cells. In addition, the individuals with AICDA mutations, but not UNG-deficient patients, displayed Tregs with defective suppressive capacity that correlated with increases in circulating T follicular helper cells and enhanced cytokine production. We conclude that SHM, but not CSR, regulates peripheral B cell tolerance through the production of mutated antibodies that clear antigens and prevent sustained interleukin secretions that interfere with Treg functio

Decreased somatic hypermutation induces an impaired peripheral B cell tolerance checkpoint

Patients with mutations in AICDA, which encodes activation-induced cytidine deaminase (AID), display an impaired peripheral B cell tolerance. AID mediates class-switch recombination (CSR) and somatic hypermutation (SHM) in B cells, but the mechanism by which AID prevents the accumulation of autoreactive B cells in blood is unclear. Here, we analyzed B cell tolerance in AID-deficient patients, patients with autosomal dominant AID mutations (AD-AID), asymptomatic AICDA heterozygotes (AID+/-), and patients with uracil N-glycosylase (UNG) deficiency, which impairs CSR but not SHM. The low frequency of autoreactive mature naive B cells in UNG-deficient patients resembled that of healthy subjects, revealing that impaired CSR does not interfere with the peripheral B cell tolerance checkpoint. In contrast, we observed decreased frequencies of SHM in memory B cells from AD-AID patients and AID+/- subjects, who were unable to prevent the accumulation of autoreactive mature naive B cells. In addition, the individuals with AICDA mutations, but not UNGdeficient patients, displayed T

Clinical spectrum and outcome of treatment for autoimmune cytopenias in rag deficiency

Univ Debrecen, Fac Med, Dept Immunol, Debrecen, HungaryHarvard Univ, Massachusetts Gen Hosp, Sch Med, Pediat Allergy & Immunol, Boston, MA USAHarvard Univ, Massachusetts Gen Hosp, Sch Med, Ctr Immunol & Inflammatory Dis, Boston, MA USAMassachusetts Gen Hosp Children, Div Pediat Allergy Immunol, Boston, MA USAUniv Tehran Med Sci, Childrens Med Ctr, Pediat Ctr Excellence, Res Ctr Immunodeficiencies, Tehran, IranMayo Clin, Lab Med & Pathol, Rochester, MN USAWeill Cornell Med Coll Qatar, Pediat, Doha, QatarSidra Med & Res Ctr, Allergy & Immunol, Doha, QatarHamad Med Corp, Doha, QatarKuwait Univ, Fac Med, Dept Pediat, Safat 13060, KuwaitAmer Univ Beirut, Ctr Infect Dis Res, Dept Pediat & Adolescent Med, Beirut, LebanonBambino Gesu Pediat Hosp, Dept Oncohematol, Stem Cell Transplant Unit, Rome, ItalyCincinnati Childrens Hosp Med Ctr, Div Bone Marrow Transplantat & Immune Deficiency, Cincinnati, OH 45229 USACincinnati Childrens Hosp Med Ctr, Cincinnati, OH 45229 USAGreat Ormond St Hosp Sick Children, Dept Paediat Immunol, London, EnglandGreat Ormond St Hosp Sick Children, Dept Paediat Immunol, London, North IrelandUC Irvine, CHOC Childrens Hosp, Pediat Hematol, Orange, CA USAChildrens Hosp Bambino Gesu, Dept Pediat, Rome, ItalyUniv Roma Tor Vergata, Sch Med, Rome, ItalyUniv Utah, Dept Pediat, Div Allergy Immunol & Rheumatol, Salt Lake City, UT USAHarvard Univ, Sch Med, Dept Pediat, Immunol Div,Boston Childrens Hosp, Boston, MA 02115 USAUniv Fed Sao Paulo, Dept Allergy Clin Immunol & Rheumatol, Sao Paulo, BrazilNIAID, Host Def Lab, NIH, 9000 Rockville Pike, Bethesda, MD 20892 USABoston Childrens Hosp, Dept Immunol, Boston, MA USAHarvard Univ, Sch Med, Boston, MA USAUniv Colorado, Sch Med, Childrens Hosp Colorado, Div Allergy & Immunol, Boulder, CO 80309 USAImmunol Outpatient Clin, Vienna, AustriaUniv Iowa, Dept Pediat, Carver Coll Med, Iowa City, IA 52242 USANatl Jewish Hlth, Dept Pediat, Div Pediat Allergy & Clin Immunol, Denver, CO USANIAID, Lab Clin Infect Dis, NIH, 9000 Rockville Pike, Bethesda, MD 20892 USAMayo Clin, Div Pediat Allergy Immunol, Rochester, MN USAAghia Sophia Childrens Hosp, Specialized Ctr, Dept Immunol Histocompatibil, Athens, GreeceAghia Sophia Childrens Hosp, Referral Ctr Primary Immunodeficiencies Pediat Im, Athens, GreeceOsped Pediat Bambino Gesu, Dept Pediat Hematol & Oncol, Rome, ItalyIRCCS Bambino Gesu Childrens Hosp, Dept Pediat Hematol & Oncol, Rome, ItalyBaylor Coll Med, Dept Pediat, Houston, TX 77030 USATexas Childrens Hosp, Sect Allergy & Immunol, Houston, TX 77030 USAErciyes Univ, Sch Med, Dept Pediat Hematol & Oncol, Kayseri, TurkeyErciyes Univ, Sch Med, Dept Pediat Immunol, Kayseri, TurkeyUniv Calif San Fransisco, Pediat Immunol & Bone Marrow Transplantat, San Francisco, CA USAChildrens Hosp Los Angeles, USC Keck Sch Med, Los Angeles, CA 90027 USAUniv Hosp Ulm, Dept Pediat & Adolescent Med, Ulm, GermanyDuke Univ, Sch Med, Div Allergy & Immunol, Durham, NC USAHarvard Univ, Sch Med, Boston Childrens Hosp, Div Immunol, Boston, MA USAUniv Fed Sao Paulo, Dept Allergy Clin Immunol & Rheumatol, Sao Paulo, BrazilWeb of Scienc

Partial RAG deficiency in humans induces dysregulated peripheral lymphocyte development and humoral tolerance defect with accumulation of T-bet+ B cells.

The recombination-activating genes (RAG) 1 and 2 are indispensable for diversifying the primary B cell receptor repertoire and pruning self-reactive clones via receptor editing in the bone marrow; however, the impact of RAG1/RAG2 on peripheral tolerance is unknown. Partial RAG deficiency (pRD) manifesting with late-onset immune dysregulation represents an 'experiment of nature' to explore this conundrum. By studying B cell development and subset-specific repertoires in pRD, we demonstrate that reduced RAG activity impinges on peripheral tolerance through the generation of a restricted primary B cell repertoire, persistent antigenic stimulation and an inflammatory milieu with elevated B cell-activating factor. This unique environment gradually provokes profound B cell dysregulation with widespread activation, remarkable extrafollicular maturation and persistence, expansion and somatic diversification of self-reactive clones. Through the model of pRD, we reveal a RAG-dependent 'domino effect' that impacts stringency of tolerance and B cell fate in the periphery

Partial RAG deficiency in humans induces dysregulated peripheral lymphocyte development and humoral tolerance defect with accumulation of T-bet+ B cells

The recombination-activating genes (RAG) 1 and 2 are indispensable for diversifying the primary B cell receptor repertoire and pruning self-reactive clones via receptor editing in the bone marrow; however, the impact of RAG1/RAG2 on peripheral tolerance is unknown. Partial RAG deficiency (pRD) manifesting with late-onset immune dysregulation represents an ‘experiment of nature’ to explore this conundrum. By studying B cell development and subset-specific repertoires in pRD, we demonstrate that reduced RAG activity impinges on peripheral tolerance through the generation of a restricted primary B cell repertoire, persistent antigenic stimulation and an inflammatory milieu with elevated B cell-activating factor. This unique environment gradually provokes profound B cell dysregulation with widespread activation, remarkable extrafollicular maturation and persistence, expansion and somatic diversification of self-reactive clones. Through the model of pRD, we reveal a RAG-dependent ‘domino effect’ that impacts stringency of tolerance and B cell fate in the periphery

Natural Killer Cells from Patients with Recombinase-Activating Gene and Non-Homologous End Joining Gene Defects Comprise a Higher Frequency of CD56(bright) NKG2A(+++) Cells, and Yet Display Increased Degranulation and Higher Perforin Content

Mutations of the recombinase-activating genes 1 and 2 (RAG1 and RAG2) in humans are associated with a broad range of phenotypes. For patients with severe clinical presentation, hematopoietic stem cell transplantation (HSCT) represents the only curative treatment; however, high rates of graft failure and incomplete immune reconstitution have been observed, especially after unconditioned haploidentical transplantation. Studies in mice have shown that Rag(-/-) natural killer (NK) cells have a mature phenotype, reduced fitness, and increased cytotoxicity. We aimed to analyze NK cell phenotype and function in patients with mutations in RAG and in non-homologous end joining (NHEJ) genes. Here, we provide evidence that NK cells from these patients have an immature phenotype, with significant expansion of CD56(bright) CD16(-/int) CD57(-) cells, yet increased degranulation and high perforin content. Correlation was observed between in vitro recombinase activity of the mutant proteins, NK cell abnormalities, and in vivo clinical phenotype. Addition of serotherapy in the conditioning regimen, with the aim of depleting the autologous NK cell compartment, may be important to facilitate engraftment and immune reconstitution in patients with RAG and NHEJ defects treated by HSCT.status: publishe