Neutrophil extracellular traps (NETs) are extracellular structures composed of chromatin and granule proteins that bind and kill microorganisms. We show that upon stimulation, the nuclei of neutrophils lose their shape, and the eu- and heterochromatin homogenize. Later, the nuclear envelope and the granule membranes disintegrate, allowing the mixing of NET components. Finally, the NETs are released as the cell membrane breaks. This cell death process is distinct from apoptosis and necrosis and depends on the generation of reactive oxygen species (ROS) by NADPH oxidase. Patients with chronic granulomatous disease carry mutations in NADPH oxidase and cannot activate this cell-death pathway or make NETs. This novel ROS-dependent death allows neutrophils to fulfill their antimicrobial function, even beyond their lifespan.

N eutrophil extracellular traps (NETs) are extracellular structures composed of chromatin and granule proteins that bind and kill microorganisms. We show that upon stimulation, the nuclei of neutrophils lose their shape, and the eu-and heterochromatin homogenize. Later, the nuclear envelope and the granule membranes disintegrate, allowing the mixing of NET components. Finally, the NETs are released as the cell membrane breaks. This cell death process is distinct from apoptosis and necrosis and depends on the generation of reactive oxygen species (ROS) by NADPH oxidase. Patients with chronic granulomatous disease carry mutations in NADPH oxidase and cannot activate this cell-death pathway or make NETs. This novel ROS-dependent death allows neutrophils to fulfi ll their antimicrobial function, even beyond their lifespan.

IntroductionMyeloperoxidase (MPO) is one of the most abundant proteins in neutrophils, accounting for 5% of the dry weight of the cell. 1 Stored in the azurophilic granules and released when neutrophils are stimulated, MPO catalyzes the oxidation of chloride and other halide ions in the presence of hydrogen peroxide 2,3 to generate hypochlorous acid and other highly reactive products that mediate efficient antimicrobial action. 4,5 Several inherited mutations and deletions in the gene encoding MPO result in decreased enzyme production and activity. 6,7 Using automated hematological devices, clinicians can distinguish between partial and complete MPO deficiencies. 8 MPO deficiency is reported to have an incidence of 1 in 2000-4000 in the United States and Europe and 1 in 55 000 in Japan. 9-13 Candida infections are common in MPO-deficient patients, especially in those that also develop diabetes. 9,14-18 Occasionally, serious infectious or inflammatory complications have been observed in completely MPOdeficient patients as well. 8 Consistently, MPO knockout mice are susceptible to particular bacterial and fungal infections. 19 Neutrophil extracellular traps (NETs) are part of the neutrophil response to microbes. Activated neutrophils die and release these structures composed of decondensed chromatin and antimicrobial proteins 20,21 that trap and inhibit a broad range of microbes. 22 Little is known about the molecular mechanism that regulates NET formation, making the antimicrobial role of NETs in vivo difficult to assess.Interestingly, neutrophils from chronic granulomatous disease (CGD) patients fail to make NETs. 20 CGD is caused by mutations that disrupt the ability of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to generate superoxide, which dismutates to hydrogen peroxide, the substrate of MPO. CGD patients are prone to recurrent and severe infections, as well as to persistent inflammation that can occur independently of infection. [23][24][25] NET formation by CGD neutrophils is restored by the addition of exogenous hydrogen peroxide, indicating that reactive oxygen species are required for NET formation. 20 Here we show that MPO is necessary for making NETs and suggest that defective NET formation may undermine host defense in patients lacking MPO. Methods Donor consentAll donors gave consent to blood drawing in accordance with the Declaration of Helsinki and to functional and genetic analysis. Samples were collected with approval from the ethical committees at each institution. Neutrophil isolationNeutrophils were isolated by centrifuging heparinized venous blood over Histopaque 1119 (Sigma-Aldrich) and subsequently over a discontinuous Percoll (Amersham Biosciences) gradient as described previously. 20 Cells were stored in Hank buffered salt solution (-) or Dulbecco phosphatebuffered saline (-), without calcium or magnesium, before experiments. NET formation and visualizationNeutrophils (5 ϫ 10 4 ) were seeded per well in 24-well tissue culture plates, in Hanks buffered salt solution (...

Background The genetic etiologies of the hyper-IgE syndromes are diverse. Approximately 60-70% of patients with hyper-IgE syndrome have dominant mutations in STAT3, and a single patient was reported to have a homozygous TYK2 mutation. In the remaining hyper-IgE syndrome patients, the genetic etiology has not yet been identified. Methods We performed genome-wide single nucleotide polymorphism analysis for nine subjects with autosomal recessive hyper-IgE syndrome to locate copy number variations and homozygous haplotypes. Homozygosity mapping was performed with twelve subjects from seven additional families. The candidate gene was analyzed by genomic and cDNA sequencing to identify causative alleles in a total of 27 patients with autosomal recessive hyper-IgE syndrome. Findings Subtelomeric microdeletions were identified in six subjects at the terminus of chromosome 9p. In all patients the deleted interval involved DOCK8, encoding a protein implicated in the regulation of the actin cytoskeleton. Sequencing of subjects without large deletions revealed 16 patients from nine unrelated families with distinct homozygous mutations in DOCK8 causing premature termination, frameshift, splice site disruption, single exon- and micro-deletions. DOCK8 deficiency was associated with impaired activation of CD4+ and CD8+ T cells. Interpretation Autosomal recessive mutations in DOCK8 are responsible for many, though not all, cases of autosomal recessive hyper-IgE syndrome. DOCK8 disruption is associated with a phenotype of severe cellular immunodeficiency characterized by susceptibility to viral infections, atopic eczema, defective T cell activation and TH17 cell differentiation; and impaired eosinophil homeostasis and dysregulation of IgE.