Key Points Human CARD9 deficiency is characterized by a selective neutrophil killing defect, resulting in invasive candidiasis.

BackgroundThe genetic cause of primary immunodeficiency disease (PID) carries prognostic information.ObjectiveWe conducted a whole-genome sequencing study assessing a large proportion of the NIHR BioResource–Rare Diseases cohort.MethodsIn the predominantly European study population of principally sporadic unrelated PID cases (n = 846), a novel Bayesian method identified nuclear factor κB subunit 1 (NFKB1) as one of the genes most strongly associated with PID, and the association was explained by 16 novel heterozygous truncating, missense, and gene deletion variants. This accounted for 4% of common variable immunodeficiency (CVID) cases (n = 390) in the cohort. Amino acid substitutions predicted to be pathogenic were assessed by means of analysis of structural protein data. Immunophenotyping, immunoblotting, and ex vivo stimulation of lymphocytes determined the functional effects of these variants. Detailed clinical and pedigree information was collected for genotype-phenotype cosegregation analyses.ResultsBoth sporadic and familial cases demonstrated evidence of the noninfective complications of CVID, including massive lymphadenopathy (24%), unexplained splenomegaly (48%), and autoimmune disease (48%), features prior studies correlated with worse clinical prognosis. Although partial penetrance of clinical symptoms was noted in certain pedigrees, all carriers have a deficiency in B-lymphocyte differentiation. Detailed assessment of B-lymphocyte numbers, phenotype, and function identifies the presence of an increased CD21low B-cell population. Combined with identification of the disease-causing variant, this distinguishes between healthy subjects, asymptomatic carriers, and clinically affected cases.ConclusionWe show that heterozygous loss-of-function variants in NFKB1 are the most common known monogenic cause of CVID, which results in a temporally progressive defect in the formation of immunoglobulin-producing B cells.

Key Points Activated neutrophils can suppress T-cell proliferation in a CD11b-dependent multistep process involving ROS production and degranulation. MDSC activity results in nonapoptotic T-cell damage.

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The NLRP3 inflammasome can be activated by pathogen-associated molecular patterns or endogenous danger-associated molecular patterns. The activation of the NLRP3 inflammasome results in proteolytic activation and secretion of cytokines of the interleukin-1 (IL-1) family. The precise mode of activation of the NLRP3 inflammasome is still elusive, but has been postulated to be mediated by reactive oxygen species (ROS) generated by an NADPH oxidase. Using primary cells from chronic granulomatous disease (CGD) patients lacking expression of p22 phox , a protein that is required for the function of Nox1-4, we show that cells lacking NADPH oxidase activity are capable of secreting normal amounts of IL-1␤. Thus, we provide evidence that activation of the NLRP3 inflammasome does not depend on ROS generated from an NADPH oxidase. (Blood. 2010;115(26): 5398-5400) IntroductionInflammasomes are specialized intracellular protein complexes responsible for regulating the proteolytic activation of proinflammatory cytokines of the interleukin-1 (IL-1) family. 1 The central components of inflammasomes, the Nod-like receptor (NLR) proteins, act as sensors for exogenous (microbial) or endogenous danger signals. Importantly, inappropriate activation of inflammasomes, due to activating mutations in the NLRs or an excess of danger signals can lead to autoinflammatory disorders such as chronic infantile neurologic cutaneous and articular syndrome, or the more common reactions in gout. 1 The best-studied NLR, NLRP3, forms inflammasomes that mediate the release of IL-1␤ and related cytokines by, for example, macrophages. The NLRP3 inflammasome can be activated by pathogen-associated molecular patterns such as lipopolysaccharide (LPS) or muramyl dipeptide, or endogenous danger-associated molecular patterns such as uric acid. 1 The precise mode of activation of the NLRP3 inflammasome is still elusive, but it has been postulated, in reports by Dostert et al, to be dependent on reactive oxygen species (ROS) generated by an NADPH oxidase. 2,3 In these reports, the authors show an inhibitory effect on IL-1␤ secretion by knockdown of p22 phox , a protein that is part of the catalytic core of several NADPH oxidases.The catalytic core of NADPH oxidases contains a member of the Nox family of proteins. 4 All members of the Nox1-4 subfamily form a heterodimer with the common p22 phox subunit. In the case of Nox2, p22 phox functions as a docking site for the regulatory protein p47 phox , and indirectly for p67 phox , and p40 phox ; the small GTPase Rac binds to p67 phox and serves as a switch for Nox2 activation. 4 For Nox1 and 3, p47 phox and p67 phox homologs are probably involved in this activation. 4 Nox4 is believed not to be regulated by p47 phox and p67 phox or their homologs, and p22 phox is not a conditio sine qua non for its activity but Nox4 activity seems to be clearly enhanced by association with p22 phox4 . The best-studied NADPH oxidase is the phagocyte NADPH oxidase, a microbicidal enzyme that contains Nox2 (gp91 phox ) and p22 phox an...

A combined immunodeficiency with severe infections, inflammation, and allergy caused by ARPC1B deficiency To the Editor:Recently, a novel syndrome of combined immunodeficiency, allergy, and ''auto''inflammation caused by mutations in the ARPC1B gene has been reported. [1][2][3][4] Analysis of patient-derived

EXTL3 regulates the biosynthesis of heparan sulfate (HS), important for both skeletal development and hematopoiesis, through the formation of HS proteoglycans (HSPGs). By whole-exome sequencing, we identified homozygous missense mutations c.1382C>T, c.1537C>T, c.1970A>G, and c.2008T>G in EXTL3 in nine affected individuals from five unrelated families. Notably, we found the identical homozygous missense mutation c.1382C>T (p.Pro461Leu) in four affected individuals from two unrelated families. Affected individuals presented with variable skeletal abnormalities and neurodevelopmental defects. Severe combined immunodeficiency (SCID) with a complete absence of T cells was observed in three families. EXTL3 was most abundant in hematopoietic stem cells and early progenitor T cells, which is in line with a SCID phenotype at the level of early T cell development in the thymus. To provide further support for the hypothesis that mutations in EXTL3 cause a neuro-immuno-skeletal dysplasia syndrome, and to gain insight into the pathogenesis of the disorder, we analyzed the localization of EXTL3 in fibroblasts derived from affected individuals and determined glycosaminoglycan concentrations in these cells as well as in urine and blood. We observed abnormal glycosaminoglycan concentrations and increased concentrations of the non-sulfated chondroitin disaccharide D0a0 and the disaccharide D0a4 in serum and urine of all analyzed affected individuals. In summary, we show that biallelic mutations in EXTL3 disturb glycosaminoglycan synthesis and thus lead to a recognizable syndrome characterized by variable expression of skeletal, neurological, and immunological abnormalities.

A girl presented during childhood with a single course of extensive chickenpox and moderate albeit recurrent pneumonia in the presence of idiopathic CD4 ؉ T lymphocytopenia (ICL). Her clinical condition remained stable over the past 10 years without infections, any granulomatous disease, or autoimmunity. Immunophenotyping demonstrated strongly reduced naive T and B cells with intact proliferative capacity. Antibody reactivity on in vivo immunizations was normal. T-cell receptor-V␤ repertoire was polyclonal with a very low content of T-cell receptor excision circles (TRECs IntroductionSelective depletion of T lymphocytes is common in both primary and secondary immunodeficiencies. Idiopathic CD4 ϩ T lymphocytopenia (ICL) is defined by an unexplained persistent CD4 ϩ T lymphocyte count of Ͻ 300 cells/L or Ͻ 20% of the total T-cell count. 1 Since the discovery of human retroviruses, sporadic ICL patients were recognized with a CD4 ϩ lymphocytopenia not infected by HIV or HTLV-1. 2-7 Smith et al reviewed 230179 cases from the CDC AIDS Reporting System and described 47 ICL patients. 2,3 Of these cases, only 3 (6%) were asymptomatic. Screening of healthy blood donors confirmed a low prevalence of ICL of 0.2%-0.6%. 4,5 The disease may have a transient nature over the years but mostly persists. 3 The immunologic parameters of ICL consist of a prolonged decrease in CD4 ϩ T cell numbers, sometimes with a concomitant decrease in CD8 ϩ T cells and B cells as well. Immunoglobulin levels are normal, 2-5 which helps to distinguish ICL from Common Variable Immunodeficiency (CVID). 1,6 Although function declines with age, thymic output is well maintained into late adulthood. 7-9 Thymic size correlates with numbers of CD4 ϩ CD45RA ϩ naive T cells. At very young age T lymphocytopenia is often caused by congenital defects resulting in severe combined immunodeficiency syndromes (SCID). 10 Null mutations in RAG1 or RAG2 account for 70% of SCID cases with the classic T Ϫ B Ϫ SCID phenotype. 10 Hypomorphic mutations with residual RAG activity occur in typical Omenn syndrome, 10 or rare cases with lympocytopenia, hypogammaglobulinemia, granulomas in the skin, mucosa, internal organs and viral complications, including EBV-related lymphomas. 11,12 In the present paper, we describe hypomorphic RAG1 mutations that corresponds with mild CD4 ϩ T lymphocytopenia, normal in vitro lymphocyte function and in vivo vaccination responses. Methods Subjects and blood samplesHeparinized venous blood was collected from healthy (age-matched) donors, patient and family members. The study was approved by the institutional medical ethical committee and informed consent for the research purpose described was obtained from the parents of the child and age-matched controls in accordance with standards of the 1964 declaration of Helsinki. Lymphocyte phenotypingAbsolute numbers of T cells, B cells, and NK cells were determined with Multitest 6-color (FACSCantoII; BD-Biosciences). For T-and B-cell subset analysis directly conjugated monoclonal antibodies (MoAbs) ...