Neutrophils activated by membrane attack complexes increase the permeability of melanoma blood vessels.

The microenvironment of malignant melanomas defines the properties of tumor blood vessels and regulates infiltration and vascular dissemination of immune and cancer cells, respectively. Previous research in other cancer entities suggested the complement system as an essential part of the tumor microenvironment. Here, we confirm activation of the complement system in samples of melanoma patients and murine melanomas. We identified the tumor endothelium as the starting point of the complement cascade. Generation of complement-derived C5a promoted the recruitment of neutrophils. Upon contact with the vascular endothelium, neutrophils were further activated by complement membrane attack complexes (MACs). MAC-activated neutrophils release neutrophil extracellular traps (NETs). Close to the blood vessel wall, NETs opened the endothelial barrier as indicated by an enhanced vascular leakage. This facilitated the entrance of melanoma cells into the circulation and their systemic spread. Depletion of neutrophils or lack of MAC formation in complement component 6 (C6)-deficient animals protected the vascular endothelium and prevented vascular intravasation of melanoma cells. Our data suggest that inhibition of MAC-mediated neutrophil activation is a potent strategy to abolish hematogenous dissemination in melanoma.

Multisystem inflammation and susceptibility to viral infections in human ZNFX1 deficiency.

BACKGROUND: Recognition of viral nucleic acids is one of the primary triggers for a type I interferon-mediated antiviral immune response. Inborn errors of type I interferon immunity can be associated with increased inflammation and/or increased susceptibility to viral infections as a result of dysbalanced interferon production. NFX1-type zinc finger-containing 1 (ZNFX1) is an interferon-stimulated double-stranded RNA sensor that restricts the replication of RNA viruses in mice. The role of ZNFX1 in the human immune response is not known. OBJECTIVE: We studied 15 patients from 8 families with an autosomal recessive immunodeficiency characterized by severe infections by both RNA and DNA viruses and virally triggered inflammatory episodes with hemophagocytic lymphohistiocytosis-like disease, early-onset seizures, and renal and lung disease. METHODS: Whole exome sequencing was performed on 13 patients from 8 families. We investigated the transcriptome, posttranscriptional regulation of interferon-stimulated genes (ISGs) and predisposition to viral infections in primary cells from patients and controls stimulated with synthetic double-stranded nucleic acids. RESULTS: Deleterious homozygous and compound heterozygous ZNFX1 variants were identified in all 13 patients. Stimulation of patient-derived primary cells with synthetic double-stranded nucleic acids was associated with a deregulated pattern of expression of ISGs and alterations in the half-life of the mRNA of ISGs and also associated with poorer clearance of viral infections by monocytes. CONCLUSION: ZNFX1 is an important regulator of the response to double-stranded nucleic acids stimuli following viral infections. ZNFX1 deficiency predisposes to severe viral infections and a multisystem inflammatory disease.

Different approaches to long-term treatment of aHUS due to MCP mutations: a multicenter analysis.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a rare, life-threatening microangiopathy, frequently causing kidney failure. Inhibition of the terminal complement complex with eculizumab is the only licensed treatment but mostly requires long-term administration and risks severe side effects. The underlying genetic cause of aHUS is thought to influence the severity of initial and recurring episodes, with milder courses in patients with mutations in membrane cofactor protein (MCP). METHODS: Twenty pediatric cases of aHUS due to isolated heterozygous MCP mutations were reported from 12 German pediatric nephrology centers to describe initial presentation, timing of relapses, treatment, and kidney outcome. RESULTS: The median age of onset was 4.6 years, with a female to male ratio of 1:3. Without eculizumab maintenance therapy, 50% (9/18) of the patients experienced a first relapse after a median period of 3.8 years. Kaplan-Meier analysis showed a relapse-free survival of 93% at 1 year. Four patients received eculizumab long-term treatment, while 3 patients received short courses. We could not show a benefit from complement blockade therapy on long term kidney function, independent of short-term or long-term treatment. To prevent 1 relapse with eculizumab, the theoretical number-needed-to-treat (NNT) was 15 for the first year and 3 for the first 5 years after initial presentation. CONCLUSION: Our study shows that heterozygous MCP mutations cause aHUS with a risk of first relapse of about 10% per year, resulting in large NNTs for prevention of relapses with eculizumab. More studies are needed to define an optimal treatment schedule for patients with MCP mutations to minimize the risks of the disease and treatment.

The MFHR1 Fusion Protein Is a Novel Synthetic Multitarget Complement Inhibitor with Therapeutic Potential.

The complement system is essential for host defense, but uncontrolled complement system activation leads to severe, mostly renal pathologies, such as atypical hemolytic uremic syndrome or C3 glomerulopathy. Here, we investigated a novel combinational approach to modulate complement activation by targeting C3 and the terminal pathway simultaneously. The synthetic fusion protein MFHR1 links the regulatory domains of complement factor H (FH) with the C5 convertase/C5b-9 inhibitory fragment of the FH-related protein 1. In vitro, MFHR1 showed cofactor and decay acceleration activity and inhibited C5 convertase activation and C5b-9 assembly, which prevented C3b deposition and reduced C3a/C5a and C5b-9 generation. Furthermore, this fusion protein showed the ability to escape deregulation by FH-related proteins and form multimeric complexes with increased inhibitory activity. In addition to substantially inhibiting alternative and classic pathway activation, MFHR1 blocked hemolysis mediated by serum from a patient with aHUS expressing truncated FH. In FH-/- mice, MFHR1 administration augmented serum C3 levels, reduced abnormal glomerular C3 deposition, and ameliorated C3 glomerulopathy. Taking the unique design of MFHR1 into account, we suggest that the combination of proximal and terminal cascade inhibition together with the ability to form multimeric complexes explain the strong inhibitory capacity of MFHR1, which offers a novel basis for complement therapeutics.

Ribavirin therapy of hepatitis E infection may cause hyporegenerative anemia in pediatric renal transplant patients.

HEV infection can lead to chronic hepatitis in immunosuppressed patients; extrahepatic manifestations are rarely seen. Here, we report a 13-year-old renal transplant patient with chronic hepatitis E and renal involvement. Ribavirin therapy led to temporary virus clearance and amelioration of kidney function. However, ribavirin therapy caused severe hyporegenerative anemia, which has so far only been reported in patients treated with a combination of ribavirin and interferon alpha.

Presentation of pediatric Henoch-Schönlein purpura nephritis changes with age and renal histology depends on biopsy timing.

BACKGROUND: This study correlates the clinical presentation of Henoch-Schönlein purpura nephritis (HSPN) with findings on initial renal biopsy. METHODS: Data from 202 pediatric patients enrolled in the HSPN registry of the German Society of Pediatric Nephrology reported by 26 centers between 2008 and 2014 were analyzed. All biopsy reports were re-evaluated for the presence of cellular crescents or chronic pathological lesions (fibrous crescents, glomerular sclerosis, tubular atrophy >5%, and interstitial fibrosis >5%). RESULTS: Patients with HSPN with cellular glomerular crescents were biopsied earlier after onset of nephritis (median 24 vs 36 days, p = 0.04) than those without, whereas patients with chronic lesions were biopsied later (57 vs 19 days, p < 0.001) and were older (10.3 vs 8.6 years, p = 0.01) than those without. Patients biopsied more than 30 days after the onset of HSPN had significantly more chronic lesions (52 vs 22%, p < 0.001), lower eGFR (88 vs 102 ml/min/1.73m2, p = 0.01), but lower proteinuria (2.3 vs 4.5 g/g, p < 0.0001) than patients biopsied earlier. Children above 10 years of age had lower proteinuria (1.98 vs 4.58 g/g, p < 0.001), lower eGFR (86 vs 101 ml/min/1.73m2, p = 0.002) and were biopsied significantly later after onset of nephritis (44 vs 22 days, p < 0.001) showing more chronic lesions (45 vs 30%, p = 0.03). Proteinuria and renal function at presentation decreased with age. CONCLUSIONS: In summary, we find an age-dependent presentation of HSPN with a more insidious onset of non-nephrotic proteinuria, impaired renal function, longer delay to biopsy, and more chronic histopathological lesions in children above the age of 10 years. Thus, HSPN presents more like Immunoglobulin A (IgA) nephritis in older than in younger children.

Treating C3 glomerulopathy with eculizumab.

BACKGROUND: C3 glomerulopathy (C3G) is a rare, but severe glomerular disease with grim prognosis. The complex pathogenesis is just unfolding, and involves acquired as well as inherited dysregulation of the alternative pathway of the complement cascade. Currently, there is no established therapy. Treatment with the C5 complement inhibitor eculizumab may be a therapeutic option. However, due to rarity of the disease, parameters predicting treatment response remain largely unknown. METHODS: Seven patients with C3G (five with C3 glomerulonephritis and two with dense deposit disease) were treated with eculizumab. Subjects underwent biopsy before enrollment. The histopathology, clinical data, and response to eculizumab treatment were analyzed. The key parameters to determine outcome were changes of serum creatinine and urinary protein over time. RESULTS: After treatment with eculizumab, four subjects showed significantly improved or stable renal function and urinary protein. A positive response occurred between 2 weeks and 6 months after therapy initiation. One subject (with allograft recurrent C3 glomerulonephritis) initially showed a positive response, but relapsed when eculizumab was discontinued, and did not respond after re-initiation of treatment. Two subjects showed impaired renal function and increasing urinary protein despite therapy with eculizumab. CONCLUSIONS: Eculizumab may be a therapeutic option for a subset of C3G patients. The response to eculizumab is heterogeneous, and early as well as continuous treatment may be necessary to prevent disease progression. These findings emphasize the need for studies identifying genetic and functional complement abnormalities that may help to guide eculizumab treatment and predict response.

[Access to Early Childhood Interventions in Children̛s Hospital: Screening as Clinical Routine Procedure - Exploration and Transfer by a Specialized Team]. / Zugang zu Frühen Hilfen in der Kinderklinik: Belastungsscreening als klinische Routine ­ differenzierte Exploration und Vermittlung durch das Fachteam.

BACKGROUND: In order to prevent risks associated with insufficient family care, it is mandatory to provide early childhood interventions for parents unable to cope with their young children in best time. Children̛s hospitals represent one pillar that hasn´t been fully explored yet. METHODS: As a proof-of-concept, we performed a study to determine the feasibility of a standardized risk assessment tool during routine work of doctors and nurses in a university department. RESULTS: Our data indicate that a standardized screen to assess stress is powerful in identifying stressed parents, especially those with children under the age of one year. In this context, psychosocial stress in families with newborns was most frequently indicated. The placement rates into early childhood interventions (8.5%) and youth welfare services (11.3%) correspond to the literature. DISCUSSION AND CONCLUSION: The standardized risk assessment tool can be used as a "call button" and delivers a basis for further differentiated exploration of the families by a specialized team and might be used to deliver services for these families. In summary children's hospitals might be useful to provide a low-threshold access into early childhood interventions.

Moss-Produced, Glycosylation-Optimized Human Factor H for Therapeutic Application in Complement Disorders.

Genetic defects in complement regulatory proteins can lead to severe renal diseases, including atypical hemolytic uremic syndrome and C3 glomerulopathies, and age-related macular degeneration. The majority of the mutations found in patients with these diseases affect the glycoprotein complement factor H, the main regulator of the alternative pathway of complement activation. Therapeutic options are limited, and novel treatments, specifically those targeting alternative pathway activation, are highly desirable. Substitution with biologically active factor H could potentially treat a variety of diseases that involve increased alternative pathway activation, but no therapeutic factor H is commercially available. We recently reported the expression of full-length recombinant factor H in moss (Physcomitrella patens). Here, we present the production of an improved moss-derived recombinant human factor H devoid of potentially immunogenic plant-specific sugar residues on protein N-glycans, yielding approximately 1 mg purified moss-derived human factor H per liter of initial P. patens culture after a multistep purification process. This glycosylation-optimized factor H showed full in vitro complement regulatory activity similar to that of plasma-derived factor H and efficiently blocked LPS-induced alternative pathway activation and hemolysis induced by sera from patients with atypical hemolytic uremic syndrome. Furthermore, injection of moss-derived factor H reduced C3 deposition and increased serum C3 levels in a murine model of C3 glomerulopathy. Thus, we consider moss-produced recombinant human factor H a promising pharmaceutical product for therapeutic intervention in patients suffering from complement dysregulation.

DNAH11 Localization in the Proximal Region of Respiratory Cilia Defines Distinct Outer Dynein Arm Complexes.

Primary ciliary dyskinesia (PCD) is a recessively inherited disease that leads to chronic respiratory disorders owing to impaired mucociliary clearance. Conventional transmission electron microscopy (TEM) is a diagnostic standard to identify ultrastructural defects in respiratory cilia but is not useful in approximately 30% of PCD cases, which have normal ciliary ultrastructure. DNAH11 mutations are a common cause of PCD with normal ciliary ultrastructure and hyperkinetic ciliary beating, but its pathophysiology remains poorly understood. We therefore characterized DNAH11 in human respiratory cilia by immunofluorescence microscopy (IFM) in the context of PCD. We used whole-exome and targeted next-generation sequence analysis as well as Sanger sequencing to identify and confirm eight novel loss-of-function DNAH11 mutations. We designed and validated a monoclonal antibody specific to DNAH11 and performed high-resolution IFM of both control and PCD-affected human respiratory cells, as well as samples from green fluorescent protein (GFP)-left-right dynein mice, to determine the ciliary localization of DNAH11. IFM analysis demonstrated native DNAH11 localization in only the proximal region of wild-type human respiratory cilia and loss of DNAH11 in individuals with PCD with certain loss-of-function DNAH11 mutations. GFP-left-right dynein mice confirmed proximal DNAH11 localization in tracheal cilia. DNAH11 retained proximal localization in respiratory cilia of individuals with PCD with distinct ultrastructural defects, such as the absence of outer dynein arms (ODAs). TEM tomography detected a partial reduction of ODAs in DNAH11-deficient cilia. DNAH11 mutations result in a subtle ODA defect in only the proximal region of respiratory cilia, which is detectable by IFM and TEM tomography.

ARMC4 mutations cause primary ciliary dyskinesia with randomization of left/right body asymmetry.

The motive forces for ciliary movement are generated by large multiprotein complexes referred to as outer dynein arms (ODAs), which are preassembled in the cytoplasm prior to transport to the ciliary axonemal compartment. In humans, defects in structural components, docking complexes, or cytoplasmic assembly factors can cause primary ciliary dyskinesia (PCD), a disorder characterized by chronic airway disease and defects in laterality. By using combined high resolution copy-number variant and mutation analysis, we identified ARMC4 mutations in twelve PCD individuals whose cells showed reduced numbers of ODAs and severely impaired ciliary beating. Transient suppression in zebrafish and analysis of an ENU mouse mutant confirmed in both model organisms that ARMC4 is critical for left-right patterning. We demonstrate that ARMC4 is an axonemal protein that is necessary for proper targeting and anchoring of ODAs.

Successful therapy of C3Nef-positive C3 glomerulopathy with plasma therapy and immunosuppression.

BACKGROUND: C3 glomerulopathies (C3G) are characterized by uncontrolled activation of the alternative pathway of complement. In most patients these diseases progress towards end-stage renal disease, and the risk of recurrence after renal transplantation is high. In the majority of patients, only antibodies against the C3 convertase, termed C3Nef, can be found as a potential pathogenic factor. Although a large variety of therapeutic approaches have been used, no generally accepted therapy exists. METHODS: In four consecutive patients with C3G in whom all known complement factor mutations were excluded and only C3Nef could be identified as a potential cause of disease, a multimodal therapeutic regimen with plasma therapy, corticosteroids and mycophenolate mofetil was used. RESULTS: The multimodal regimen achieved normalization of renal function in all four patients, with complete remission in two patients and a distinct reduction of proteinuria in the other two patients. The single patient with C3 glomerulonephritis (C3GN) and marked terminal complement complex elevation only showed partial remission; further improvement was achieved following the addition of eculizumab to the therapeutic regimen. Repeatedly measured C3Nef levels did not correlate with disease course or therapeutic response in any of the patients. CONCLUSIONS: As this multimodal therapeutic approach was effective in all four treated patients with suspected autoimmune etiology of C3G, it offers a treatment option for severely affected patients with this rare disease until more specific regimens are available.

Ciliary beat pattern and frequency in genetic variants of primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a rare genetic disorder leading to recurrent respiratory tract infections. High-speed video-microscopy analysis (HVMA) of ciliary beating, currently the first-line diagnostic tool for PCD in most centres, is challenging because recent studies have expanded the spectrum of HVMA findings in PCD from grossly abnormal to very subtle. The objective of this study was to describe the diversity of HVMA findings in genetically confirmed PCD individuals. HVMA was performed as part of the routine work-up of individuals with suspected PCD. Subsequent molecular analysis identified biallelic mutations in the PCD-related genes of 66 individuals. 1072 videos of these subjects were assessed for correlation with the genotype. Biallelic mutations (19 novel) were found in 17 genes: DNAI1, DNAI2, DNAH5, DNAH11, CCDC103, ARMC4, KTU/DNAAF2, LRRC50/DNAAF1, LRRC6, DYX1C1, ZMYND10, CCDC39, CCDC40, CCDC164, HYDIN, RSPH4A and RSPH1. Ciliary beat pattern variations correlated well with the genetic findings, allowing the classification of typical HVMA findings for different genetic groups. In contrast, analysis of ciliary beat frequency did not result in additional diagnostic impact. In conclusion, this study provides detailed knowledge about the diversity of HVMA findings in PCD and may therefore be seen as a guide to the improvement of PCD diagnostics.

Distinct localization of septin proteins to ciliary sub-compartments in airway epithelial cells.

Mucociliary clearance of the airways is accomplished by cilia-mediated laminar mucus flow along the planar epithelial surface. Maintenance of the highly specific architecture of the ciliated airway epithelium with columnar-shaped epithelial cells and tightening of the epithelial barrier is mainly attributed to the F-actin cytoskeleton. Recently, members of the highly conserved family of septin proteins have been shown to play crucial roles in ciliated tissue. These GTP-binding proteins form hetero-oligomeric complexes and assemble higher-order cytoskeletal structures such as filaments, bundles and ring-like structures such as a membrane diffusion barrier at the ciliary base. Here we analyzed the subcellular and sub-ciliary localization of various septin proteins by immunofluorescence imaging of airway epithelial cells. In addition to cytoplasmic localization we found that septins are either enriched at the apical cell cortex including the ciliary bases (septin-2, -4, -6, and -7), or show axonemal staining (septin-2, -7, -9 and -11) or specifically localize to ciliary sub-compartments (septin-8 and -9). The distinct localization of septins suggests structural functions as cytoskeletal components and as elements of the mechanical barrier at the apical cell cortex. Furthermore, the tight association of septin-8 and -9 with the ciliary compartment indicates a possible involvement in cilia-specific functions and cilia-related diseases.

Mutations in WDR19 encoding the intraflagellar transport component IFT144 cause a broad spectrum of ciliopathies.

BACKGROUND: An emerging number of clinically and genetically heterogeneous diseases now collectively termed ciliopathies have been connected to the dysfunction of primary cilia. We describe an 8-year-old girl with a complex phenotype that did not clearly match any familiar syndrome. CASE-DIAGNOSIS/TREATMENT: Hypotonia, facial dysmorphism and retardation were noted shortly after birth. Other features included short stature, mild skeletal anomalies, strabism, deafness, subdural hygroma, hepatosplenomegaly and end-stage renal failure. Renal biopsy revealed tubular atrophy, interstitial fibrosis and segmental glomerulosclerosis. After exclusion of a chromosomal abnormality by array-comparative genomic hybridization (CGH), we performed next-generation sequencing (NGS) using a customized panel that targeted 131 genes known or hypothesized to cause ciliopathies. We identified the novel homozygous WDR19 mutation c.1483G > C (p.Gly495Arg) that affects an evolutionarily highly conserved residue in the intraflagellar transport protein IFT144, is absent from databases and is predicted to be pathogenic by all bioinformatic sources used. CONCLUSION: Mutations in WDR19 encoding the intraflagellar transport component IFT144 have recently been described in single families with the clinically overlapping skeletal ciliopathies Jeune and Sensenbrenner syndromes, combined or isolated nephronophthisis (NPHP) and retinitis pigmentosa (RP) (Senior-Loken syndrome). Our patient emphasizes the usefulness and efficiency of a comprehensive NGS panel approach in patients with unclassified ciliopathies. It further suggests that WDR19 mutations can cause a broad spectrum of ciliopathies that extends to Jeune and Sensenbrenner syndromes, RP and renal NPHP-like phenotypes.

Moss-produced human complement factor H with modified glycans has an extended half-life and improved biological activity.

Most drugs that target the complement system are designed to inhibit the complement pathway at either the proximal or terminal levels. The use of a natural complement regulator such as factor H (FH) could provide a superior treatment option by restoring the balance of an overactive complement system while preserving its normal physiological functions. Until now, the systemic treatment of complement-associated disorders with FH has been deemed unfeasible, primarily due to high production costs, risks related to FH purified from donors' blood, and the challenging expression of recombinant FH in different host systems. We recently demonstrated that a moss-based expression system can produce high yields of properly folded, fully functional, recombinant FH. However, the half-life of the initial variant (CPV-101) was relatively short. Here we show that the same polypeptide with modified glycosylation (CPV-104) achieves a pharmacokinetic profile comparable to that of native FH derived from human serum. The treatment of FH-deficient mice with CPV-104 significantly improved important efficacy parameters such as the normalization of serum C3 levels and the rapid degradation of C3 deposits in the kidney compared to treatment with CPV-101. Furthermore, CPV-104 showed comparable functionality to serum-derived FH in vitro, as well as similar performance in ex vivo assays involving samples from patients with atypical hemolytic uremic syndrome, C3 glomerulopathy and paroxysomal nocturnal hematuria. CPV-104 - the human FH analog expressed in moss - will therefore allow the treatment of complement-associated human diseases by rebalancing instead of inhibiting the complement cascade.

Mutations in DNAH5 cause primary ciliary dyskinesia and randomization of left-right asymmetry.

Primary ciliary dyskinesia (PCD, MIM 242650) is characterized by recurrent infections of the respiratory tract due to reduced mucociliary clearance and by sperm immobility. Half of the affected offspring have situs inversus (reversed organs), which results from randomization of left-right (LR) asymmetry. We previously localized to chromosome 5p a PCD locus containing DNAH5, which encodes a protein highly similar to the Chlamydomonas gamma-dynein heavy chain. Here we characterize the full-length 14-kb transcript of DNAH5. Sequence analysis in individuals with PCD with randomization of LR asymmetry identified mutations resulting in non-functional DNAH5 proteins.

Deletions and point mutations of LRRC50 cause primary ciliary dyskinesia due to dynein arm defects.

Genetic defects affecting motility of cilia and flagella cause chronic destructive airway disease, randomization of left-right body asymmetry, and, frequently, male infertility in primary ciliary dyskinesia (PCD). The most frequent defects involve outer and inner dynein arms (ODAs and IDAs) that are large multiprotein complexes responsible for cilia-beat generation and regulation, respectively. Here, we demonstrate that large genomic deletions, as well as point mutations involving LRRC50, are responsible for a distinct PCD variant that is characterized by a combined defect involving assembly of the ODAs and IDAs. Functional analyses showed that LRRC50 deficiency disrupts assembly of distally and proximally DNAH5- and DNAI2-containing ODA complexes, as well as DNALI1-containing IDA complexes, resulting in immotile cilia. On the basis of these findings, we assume that LRRC50 plays a role in assembly of distinct dynein-arm complexes.

Impact of neutrophil extracellular traps on fluid properties, blood flow and complement activation.

Introduction: The intravascular formation of neutrophil extracellular traps (NETs) is a trigger for coagulation and blood vessel occlusion. NETs are released from neutrophils as a response to strong inflammatory signals in the course of different diseases such as COVID-19, cancer or antiphospholipid syndrome. NETs are composed of large, chromosomal DNA fibers decorated with a variety of proteins such as histones. Previous research suggested a close mechanistic crosstalk between NETs and the coagulation system involving the coagulation factor XII (FXII), von Willebrand factor (VWF) and tissue factor. However, the direct impact of NET-related DNA fibers on blood flow and blood aggregation independent of the coagulation cascade has remained elusive. Methods: In the present study, we used different microfluidic setups in combination with fluorescence microscopy to investigate the influence of neutrophil-derived extracellular DNA fibers on blood rheology, intravascular occlusion and activation of the complement system. Results: We found that extended DNA fiber networks decelerate blood flow and promote intravascular occlusion of blood vessels independent of the plasmatic coagulation. Associated with the DNA dependent occlusion of the flow channel was the strong activation of the complement system characterized by the production of complement component 5a (C5a). Vice versa, we detected that the local activation of the complement system at the vascular wall was a trigger for NET release. Discussion: In conclusion, we found that DNA fibers as the principal component of NETs are sufficient to induce blood aggregation even in the absence of the coagulation system. Moreover, we discovered that complement activation at the endothelial surface promoted NET formation. Our data envisions DNA degradation and complement inhibition as potential therapeutic strategies in NET-induced coagulopathies.