Transmembrane Pickets Connect Cyto- and Pericellular Skeletons Forming Barriers to Receptor Engagement.

Phagocytic receptors must diffuse laterally to become activated upon clustering by multivalent targets. Receptor diffusion, however, can be obstructed by transmembrane proteins ("pickets") that are immobilized by interacting with the cortical cytoskeleton. The molecular identity of these pickets and their role in phagocytosis have not been defined. We used single-molecule tracking to study the interaction between Fcγ receptors and CD44, an abundant transmembrane protein capable of indirect association with F-actin, hence likely to serve as a picket. CD44 tethers reversibly to formin-induced actin filaments, curtailing receptor diffusion. Such linear filaments predominate in the trailing end of polarized macrophages, where receptor mobility was minimal. Conversely, receptors were most mobile at the leading edge, where Arp2/3-driven actin branching predominates. CD44 binds hyaluronan, anchoring a pericellular coat that also limits receptor displacement and obstructs access to phagocytic targets. Force must be applied to traverse the pericellular barrier, enabling receptors to engage their targets.

Kidney disease and organ transplantation in methylmalonic acidaemia.

OBJECTIVES: MMA is associated with chronic tubulointerstitial nephritis and a progressive decline in GFR. Optimal management of these children is uncertain. Our objectives were to document the pre-, peri-, and post-transplant course of all children with MMA who underwent liver or combined liver-kidney transplant in our centers. DESIGN AND METHODS: Retrospective chart review of all cases of MMA who underwent organ transplantation over the last 10 years. RESULTS: Five children with MMA underwent liver transplant (4/5) and combined liver-kidney transplant (1/5). Three were Mut0 and two had a cobalamin B disorder. Four of five were transplanted between ages 3 and 5 years. Renal dysfunction prior to transplant was seen in 2/5 patients. Post-transplant (one liver transplant and one combined transplant) renal function improved slightly when using creatinine-based GFR formula. We noticed in 2 patients a big discrepancy between creatinine- and cystatin C-based GFR calculations. One patient with no renal disease developed renal failure post-liver transplantation. Serum MMA levels have decreased in all to <300 µmol/L. Four patients remain on low protein diet, carnitine, coenzyme Q, and vitamin E post-transplant. CONCLUSIONS: MMA is a complex metabolic disorder. Renal disease can continue to progress post-liver transplant and close follow-up is warranted. More research is needed to clarify best screening GFR method in patients with MMA. Whether liver transplant alone, continued protein restriction, or the addition of antioxidants post-transplant can halt the progression of renal disease remains unclear.

The role of von Willebrand factor in thrombotic microangiopathy.

Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The disease spectrum of TMA includes, amongst others, thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS). TTP is caused by defective cleavage of von Willebrand factor (VWF), whereas aHUS is caused by overshooting complement activation and subsequent endothelial cell (EC) injury. Despite their distinct pathophysiology, the clinical manifestation of TTP and aHUS consisting of microangiopathic haemolytic anaemia and thrombocytopenia is often similar and difficult to distinguish. Recent evidence hints at both a genetic and functional link between TTP and aHUS, especially between VWF and the complement system. There is novel in vitro evidence that complement activation not only results in VWF release from ECs, but that VWF also functions as a negative complement regulator, thus protecting the EC surface from ongoing complement attack. Although contrary to previous experimental work suggesting that complement can be activated on VWF multimers, there may be an explanation in vivo that rationalizes these apparently contradictory findings, whereby a system primarily meant to regulate becomes overwhelmed or pathologic in the disease state. The importance of unravelling these recent findings for our understanding of TMA pathology becomes even more evident considering that glomerular ECs express VWF in a heterogeneous pattern with an overall decreased expression level, thus potentially leaving the glomerular ECs vulnerable to complement-mediated injury. Taken together, these findings support the concept that TTP and aHUS represent two extreme ends of a TMA disease spectrum rather than isolated disease entities.

C3 Glomerulopathy.

Recent advances in our understanding of the disease pathology of membranoproliferative glomerulonephritis has resulted in its re-classification as complement C3 glomerulopathy (C3G) and immune complex-mediated glomerulonephritis (IC-GN). The new consensus is based on its underlying pathomechanism, with a key pathogenetic role for the complement alternative pathway (AP), rather than on histomorphological characteristics. In C3G, loss of AP regulation leads to predominant glomerular C3 deposition, which distinguishes C3G from IC-GN with predominant immunoglobulin G staining. Electron microscopy further subdivides C3G into C3 glomerulonephritis and dense deposit disease depending on the presence and distribution pattern of electron-dense deposits within the glomerular filter. Mutations or autoantibodies affecting the function of AP activators or regulators, in particular the decay of the C3 convertase (C3 nephritic factor), have been detected in up to 80 % of C3G patients. The natural outcome of C3G is heterogeneous, but 50 % of patients progress slowly and reach end-stage renal disease within 10-15 years. The new classification not only marks significant advancement in the pathogenic understanding of this rare disease, but also opens doors towards more specific treatment with the potential for improved outcomes.

Therapeutic plasma exchange in children: One center's experience.

BACKGROUND: Therapeutic plasma exchange (TPE) has evolved to an accepted therapy for selected indications. However, it is technically challenging in children. Moreover, data on safety and efficacy are mainly derived from adult series. The aim of this study was to review the procedure in the context of clinical indications, effectiveness, and safety. STUDY DESIGN AND METHODS: All TPE procedures performed at a tertiary care hospital during a 12-year period (2005-2016) were retrospectively evaluated. RESULTS: Eighteen patients with a median age of 8.5 (0.2-17) years underwent a total of 280 TPE sessions. Eleven (61%) patients were treated for renal diseases. Three (17%) patients were diagnosed with neurological diseases, two had liver failure, and one patient each had sepsis and stem cell transplant-associated thrombotic microangiopathy. Seven patients (39%) were classified as American Society for Apheresis Category I, four (22%) as Category II, two (13%) each as Category III and IV, and two (13%) were not classified. Two patients with atypical hemolytic-uremic syndrome received TPE as long-term therapy over 2 and 5 years. All procedures were performed using the filtration technique and heparin anticoagulation. Twelve (67%) patients showed full or partial recovery after TPE, six had no response or an uncertain response. Minor adverse events occurred in 30/280 (10.6%) procedures, and one major complication (0.4%) was reported. CONCLUSION: TPE is a safe apheresis method in children, even when performed as a long-term therapy. Efficacy is high under selected conditions. A highly skilled and experienced staff is mandatory to ensure patient safety and efficacy.

Von Willebrand factor regulates complement on endothelial cells.

Atypical hemolytic uremic syndrome and thrombotic thrombocytopenic purpura have traditionally been considered separate entities. Defects in the regulation of the complement alternative pathway occur in atypical hemolytic uremic syndrome, and defects in the cleavage of von Willebrand factor (VWF)-multimers arise in thrombotic thrombocytopenic purpura. However, recent studies suggest that both entities are related as defects in the disease-causing pathways overlap or show functional interactions. Here we investigate the possible functional link of VWF-multimers and the complement system on endothelial cells. Blood outgrowth endothelial cells (BOECs) were obtained from 3 healthy individuals and 2 patients with Type 3 von Willebrand disease lacking VWF. Cells were exposed to a standardized complement challenge via the combination of classical and alternative pathway activation and 50% normal human serum resulting in complement fixation to the endothelial surface. Under these conditions we found the expected release of VWF-multimers causing platelet adhesion onto BOECs from healthy individuals. Importantly, in BOECs derived from patients with von Willebrand disease complement C3c deposition and cytotoxicity were more pronounced than on BOECs derived from normal individuals. This is of particular importance as primary glomerular endothelial cells display a heterogeneous expression pattern of VWF with overall reduced VWF abundance. Thus, our results support a mechanistic link between VWF-multimers and the complement system. However, our findings also identify VWF as a new complement regulator on vascular endothelial cells and suggest that VWF has a protective effect on endothelial cells and complement-mediated injury.

Akt-dependent enhanced migratory capacity of Th17 cells from children with lupus nephritis.

Th17 cells infiltrate the kidneys of patients with lupus nephritis (LN) and are critical for the pathogenesis of this disease. In this study, we show that enhanced activity of Stat3 in CD4(+)CD45RA(-)Foxp3(-) and Foxp3(low) effector T cells from children with LN correlates with increased frequencies of IL-17-producing cells within these T cell populations. The levels of retinoic acid-related orphan receptor c and IL-17 mRNA are significantly higher in PBMCs from children with LN than in those from controls. Mammalian target of rapamycin inhibition by rapamycin reduces both Stat3 activation in effector T cells and the frequency of IL-17-producing T cells in lupus patients. Complement factor C5a slightly increases the expression of IL-17 and induces activation of Akt in anti-CD3-activated lupus effector T cells. Th17 cells from children with LN exhibit high Akt activity and enhanced migratory capacity. Inhibition of the Akt signaling pathway significantly decreases Th17 cell migration. These findings indicate that the Akt signaling pathway plays a significant role in the migratory activity of Th17 cells from children with LN and suggest that therapeutic modulation of the Akt activity may inhibit Th17 cell trafficking to sites of inflammation and thus suppress chronic inflammatory processes in children with LN.

C3 Glomerulopathy and post-infectious glomerulonephritis define a disease spectrum.

BACKGROUND: Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have an atypical, severe presentation, and these exceptional cases have been linked to the dysregulation of the complement alternative pathway (CAP). There is a considerable overlap in the histopathological features of PIGN and C3 glomerulopathy (C3G), which is also associated with CAP dysregulation but has a poorer outcome. We hypothesized that PIGN and C3G define a disease spectrum, and that in the past there may be some children with C3G who were misclassified with PIGN before C3G was described as a separate disease entity. METHODS: Children with PIGN (n = 33) diagnosed between 1985 and 2010 who underwent a renal biopsy due to their unusual course were reviewed and of them, 8 were reclassified into C3G based on the current classification criteria. Outcome was based on the degree of proteinuria, C3 level, and renal function at follow-up. RESULTS: Sixteen (72.7%) children with typical PIGN recovered completely as compared to only 2 (25%) with C3G. Of note, children with "typical" PIGN had a more severe disease course at onset; however, the outcome at last follow up was favorable. CONCLUSIONS: Our results support the hypothesis that PIGN and C3G form a disease spectrum and have different long-term clinical implications and management strategies.

An international consensus approach to the management of atypical hemolytic uremic syndrome in children.

Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of complement dysregulation. This advance facilitated the development of novel, rational treatment options targeting terminal complement activation, e.g., using an anti-C5 antibody (eculizumab). We review treatment and patient management issues related to this therapeutic approach. We present consensus clinical practice recommendations generated by HUS International, an international expert group of clinicians and basic scientists with a focused interest in HUS. We aim to address the following questions of high relevance to daily clinical practice: Which complement investigations should be done and when? What is the importance of anti-factor H antibody detection? Who should be treated with eculizumab? Is plasma exchange therapy still needed? When should eculizumab therapy be initiated? How and when should complement blockade be monitored? Can the approved treatment schedule be modified? What approach should be taken to kidney and/or combined liver-kidney transplantation? How should we limit the risk of meningococcal infection under complement blockade therapy? A pressing question today regards the treatment duration. We discuss the need for prospective studies to establish evidence-based criteria for the continuation or cessation of anticomplement therapy in patients with and without identified complement mutations.

The alternative pathway of complement and the thrombotic microangiopathies.

Thrombotic microangiopathies (TMA) are disorders defined by microangiopathic hemolytic anemia, non-immune thrombocytopenia and have multi-organ involvement including the kidneys, brain, gastrointestinal, respiratory tract and skin. Emerging evidence points to the central role of complement dysregulation in leading to microvascular endothelial injury which is crucial for the development of TMAs. This key insight has led to the development of complement-targeted therapy. Eculizumab is an anti-C5 monoclonal antibody, which has revolutionized the treatment of atypical hemolytic uremic syndrome. Several other anti-complement therapeutic agents are currently in development, offering a potential armamentarium of therapies available to treat complement-mediated TMAs. The development of sensitive, reliable and easy to perform assays to monitor complement activity and therapeutic efficacy will be key to devising an individualized treatment regime with the potential of safely weaning or discontinuing treatment in the appropriate clinical setting.

Treatment of enterohemorrhagic Escherichia coli-induced hemolytic uremic syndrome (eHUS).

Treatment of enterohemorrhagic Escherichia coli-induced hemolytic uremic syndrome (eHUS) still mostly relies on supportive intensive care regimens. Antibiotic treatment, as administered to eHUS patients during the 2011 O104:H4 outbreak, may reduce the shedding period, but this may apply only to this particular strain. In any case, there is no evidence for a beneficial use in the diarrheal phase and earlier warnings that antibiotic therapy at this stage may actually increase the likelihood of HUS remain unrefuted. Plasma exchange, a frequently chosen therapy in acute atypical HUS, was not beneficial for the outbreak patients and a prospective study of 274 pediatric eHUS patients even indicates a poorer long-term outcome. As eHUS is a disease where complement plays a pathophysiological role and individual beneficial treatments had been published, eculizumab was broadly administered during the outbreak, in particular to severely ill patients. The equally good outcome of treated versus untreated patients obviously does not allow a clear-cut statement, but rather points toward an advantageous use, at least for the severe cases. Although the role of complement should not be overestimated, the use of a complement blocker--not necessarily being a therapeutic option for uncomplicated eHUS--in severe disease may actually make the difference between favorable or detrimental outcome.

Spectrum of complement-mediated thrombotic microangiopathies: pathogenetic insights identifying novel treatment approaches.

Thrombotic microangiopathy (TMA) is a rare but severe disorder characterized by endothelial cell activation and thrombus formation. It manifests with the triad of hemolytic anemia, thrombocytopenia, and organ failure. Prompt diagnosis and treatment initiation are crucial for long-term outcome. TMA often manifests subsequent to infectious events, of which (enterohemorrhagic) Escherichia coli is the most frequently reported. TMA also occurs on the background of genetic/autoimmune defects in the complement system (atypical hemolytic uremic syndrome [aHUS]) and underlying conditions, such as pregnancy, transplantation, drugs, other glomerulopathies, vasculitides, or metabolic defects. Complement activation or defects in its regulation have now been described in an increasing number of acquired diseases with TMA. Coinciding with this expanding spectrum of complement-mediated diseases, the question arises which patients might benefit from a complement-targeted therapy. Success of therapy depends on the individual contribution of complement activation in disease pathogenesis. The advent of eculizumab, a monoclonal antibody that blocks terminal complement activation, has markedly improved outcome and quality of life in patients with aHUS. This review discusses the contribution of complement and highlights its complex interaction with inflammation, coagulation, and the endothelium. Treatment experiences focusing on eculizumab therapy are discussed in detail across the emerging spectrum of complement-mediated thrombotic microangiopathies.

Enhanced activity of Akt in Teff cells from children with lupus nephritis is associated with reduced induction of tumor necrosis factor receptor-associated factor 6 and increased OX40 expression.

OBJECTIVE: The breakdown of peripheral tolerance mechanisms is central to the pathogenesis of systemic lupus erythematosus (SLE). Although true Treg cells in patients with SLE exhibit intact suppressive activity, Teff cells are resistant to suppression. The underlying mechanisms are incompletely understood. This study was undertaken to examine the Akt signaling pathway and molecules that may alter its activity in T cells in lupus patients. METHODS: The Akt pathway and its regulators were analyzed in Teff and Treg cells from children with lupus nephritis and controls using flow cytometry and real-time quantitative polymerase chain reaction. T cell proliferation was assessed by analysis of 5,6-carboxyfluorescein succinimidyl ester dilution. RESULTS: CD4+CD45RA-FoxP3(low) and FoxP3- Teff cells from children with lupus nephritis expressed high levels of activated Akt, resulting in the down-regulation of the proapoptotic protein Bim and an enhanced proliferative response. The induction of tumor necrosis factor receptor-associated factor 6 (TRAF6) was impaired, and TRAF6 levels inversely correlated with Akt activity. Although the expression of OX40 was enhanced on Teff cells from children with lupus nephritis compared to controls, OX40 stimulation failed to significantly increase TRAF6 expression in cells from patients, in contrast to those from healthy controls, but resulted in further increased Akt activation that was reversed by blockade of OX40 signaling. Moreover, inhibition of Akt signaling markedly decreased the proliferation of Teff cells from lupus patients. CONCLUSION: Our findings indicate that hyperactivation of the Akt pathway in Teff cells from children with lupus nephritis is associated with reduced induction of TRAF6 and up-regulation of OX40, which may cause Teff cell resistance to Treg cell-mediated suppression.

An audit analysis of a guideline for the investigation and initial therapy of diarrhea negative (atypical) hemolytic uremic syndrome.

BACKGROUND: In 2009, the European Paediatric Study Group for Haemolytic Uraemic Syndrome (HUS) published a clinical practice guideline for the investigation and initial therapy of diarrhea-negative HUS (now more widely referred to as atypical HUS, aHUS). The therapeutic component of the guideline (comprising early, high-volume plasmapheresis) was derived from anecdotal evidence and expert consensus, and the authors committed to auditing outcome. METHODS: Questionnaires were distributed to pediatric nephrologists across Europe, North America, and the Middle East, who were asked to complete one questionnaire per patient episode of aHUS between July 1, 2009 and December 31, 2010. Comprehensive, anonymous demographic and clinical data were collected. RESULTS: Seventy-one children were reported with an episode of aHUS during the audit period. Six cases occurred on a background of influenza A H1N1 infection. Of 71 patients, 59 (83 %) received plasma therapy within the first 33 days, of whom ten received plasma infusion only. Complications of central venous catheters occurred in 16 out of 51 patients with a catheter in-situ (31 %). Median time to enter hematological remission was 11.5 days, and eight of 71 (11 %) patients did not enter hematological remission by day 33. Twelve patients (17 %) remained dialysis dependent at day 33. CONCLUSIONS: This audit provides a snapshot of the early outcome of a group of children with aHUS in the months prior to more widespread use of eculizumab.

Need for long-term follow-up in enterohemorrhagic Escherichia coli-associated hemolytic uremic syndrome due to late-emerging sequelae.

BACKGROUND: The aim of this study was to evaluate the long-term prognosis of children with hemolytic uremic syndrome (HUS). METHODS: Over a 6-year period, 619 pediatric patients with the clinical diagnosis of HUS were registered in Austria and Germany, and a subset (n = 274) was prospectively followed up for 5 years. RESULTS: Infection with enterohemorrhagic Escherichia coli (EHEC) was confirmed in 79% of cases. Five years after diagnosis, 70% of EHEC-infected patients (95% confidence interval [CI], .63-.76) were fully recovered. The remaining 30% had persistent hypertension (9%), neurological symptoms (4%), decreased glomerular filtration rate (7%), and/or proteinuria (18%). Hypertension and proteinuria developed in a total of 18% of patients who had no sequelae 1 year after the acute phase (95% CI, 12-26). Multivariate logistic regression analysis demonstrated an association between the use of plasma therapy during acute phase and poor long-term outcome (odds ratio, 2.9-13; 95% CI, 2.4-33; P < .05), but this treatment was also used more frequently in severe cases. In contrast, the use of antibiotic therapy in the diarrheal phase and other established risk factors for developing HUS, such as Shiga toxin 2 and EHEC serotypes traditionally considered to be "high risk," were not associated with adverse long-term outcome. In particular, there was no difference between O157 and non-O157 EHEC. CONCLUSIONS: This study identified an association between the use of plasma treatment and poor long-term outcome and confirms already known risk factors for poor prognosis. Follow-up investigations for at least 5 years are recommended to detect late-emerging sequelae.

Activity of childhood lupus nephritis is linked to altered T cell and cytokine homeostasis.

PURPOSE: Standard therapy for lupus nephritis is based on non-specific immunosuppression. We aimed to identify specific alterations in T cell and cytokine homeostasis and possible associations with disease activity in children with lupus nephritis (LN). METHODS: The phenotype of circulating T cells from children with LN and healthy controls (HC) was analyzed by flow cytometry. Intracellular expression of IL-17 and INF-γ was assessed after stimulation with anti-CD3 and anti-CD28. Serum concentrations of IP10, CCL2, TGF-ß, IL-17, and IL-23 were measured by ELISA. Disease activity was determined using the Systemic Lupus Erythematosus Disease Activity Index 2000 update (SLEDAI-2K). RESULTS: Children with active LN displayed increased frequencies of effector memory CD4(+)CD45RO(+)CCR7(-) and terminal differentiated CD4(+)CD45RA(+)CCR7(-) T cells and reduced naive CD4(+)CD45RA(+)CCR7(+) T cells compared to those with inactive LN or HC. Circulating CD4(+)CXCR3(+) and CD4(+)CCR2(+) T cells correlated inversely with the renal SLEDAI-2K, whereas IP10 and CCL2 showed a positive correlation. Reduced CD4(+)Foxp3(+) T cells and serum TFG-ß levels in active LN were associated with high serum IL-17 and IL-23 levels and correlated inversely with the renal SLEDAI-2K (r = -0.5855, p = 0.0013 and r = -0.6246, p = 0.0005, respectively), whereas IL-17 and IL-23 correlated positively (r = 0.5516, p = 0.0029 and r = 0.6116, p = 0.0007, respectively). Expansion of Th17 and Th1/Th17 cells in children with LN was significantly greater than in HC (p = 0.0304 and p = 0.0067, respectively). CONCLUSION: Children with active LN display high levels of pro-inflammatory cytokines associated with an increase in effector T cells and reduction of regulatory T cells. Therapeutic regulation of the aberrant cytokine profile might specifically interrupt pathogenic mechanisms.

Manifestation of atypical hemolytic uremic syndrome caused by novel mutations in MCP.

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. Mutations in genes encoding regulators of the alternative complement pathway (CFH, MCP, C3, CFI, CFB, THBD, and CFHR1-5) are connected with this disease. Polymorphisms (SNPs) in these genes might also influence the manifestation of aHUS. We have analyzed the genes of CFH, CFI, MCP, and C3 in a cohort of 10 unrelated Czech patients with clinically diagnosed familial aHUS. Surprisingly, 4 patients had mutations only in MCP, without mutations in any of the other genes that cause aHUS. Mutations, as yet unpublished, were widely distributed over the gene (SCR2 domain, signal peptide, and cytoplasmic region). The phenotype of the patients and their close relatives (14 individuals) was also investigated. Functional examination of MCP was also provided and proved lower expression on granulocytes in all mutations. Severity of disease varied, but onset was never earlier than 5 years of age. Penetrance of disease was 50% among carriers. We found that the severity and recurrence of the disease within families varied and might also be dependent on SNPs. Mutations in the MCP gene seems to be a common etiology of aHUS in Czech patients.

Soluble VEGF receptor 1 promotes endothelial injury in children and adolescents with lupus nephritis.

BACKGROUND: Endothelial cell injury plays a key role in the pathogenesis of lupus nephritis (LN) and atherosclerosis. The aim of this study was to identify factors involved in the process of endothelial damage in children and adolescents with LN. METHODS: We evaluated the relationship between plasma vascular endothelial growth factor (VEGF), its soluble receptors sVEGFR-1 and sVEGFR-2 and markers of endothelial inflammation and injury (angiopoietin-2 and thrombomodulin, respectively) in 23 children and adolescents with LN (active LN, n = 14; inactive LN, n = 9; mean age 15 years) and 20 healthy controls (HC; mean age 12 years). RESULTS: VEGF, sVEGFR-1, angiopoietin-2 and thrombomodulin levels were significantly higher in children and adolescents with active LN than in patients in remission or HC. In active LN, however, VEGF was inversely related to sVEGFR-1 (r = -0.802, p < 0.001), angiopoietin-2 (r = -0.684, p = 0.007) and thrombomodulin (r = -0.697, p = 0.006). There was a significant positive correlation between sVEGFR-1 and thrombomodulin (r = 0.814, p < 0.0001), but sVEGFR-2 did not significantly differ between the patient groups and did not correlate with thrombomodulin (r = 0.046, p = 0.833). CONCLUSIONS: sVEGFR-1 may play an important role in promoting endothelial damage in children and adolescents with active LN and could possibly be used to monitor disease severity.

Analysis of the classical, alternative, and mannose binding lectin pathway of the complement system in the pathogenesis of oligoarticular juvenile idiopathic arthritis.

The complement system plays a role in the pathogenesis of some autoimmunopathies. This longitudinal study evaluates the contribution of the complement system in the pathogenesis of oligoarticular juvenile idiopathic arthritis (JIA). Serum of the peripheral blood and the synovial fluid were investigated for the activity of the classical (CP), the mannose binding lectin (MBL), and the alternative pathway (AP). A total of 12 samples from peripheral blood (PB) and two samples from synovial fluid (SF) of girls with oligoarticular JIA were investigated in a longitudinal observation from the time point of the diagnosis of JIA. The differences between the complement activity in the PB and in the SF were extremely statistically significant (CP and MBL: P < 0.0001; AP: < 0.0087). The activity of the CP and the MBL pathway was reduced. The AP is the main contributor in the pathogenesis of oligoarticular JIA. Anti-C5 therapy may be an option to avoid the creation of the membrane attack complex.

Eculizumab in atypical hemolytic uremic syndrome: long-term clinical course and histological findings.

Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy associated with defective regulation of the alternative complement pathway. The prognosis for patients with aHUS is poor, and plasma exchange represents the first-line therapy. Eculizumab is a humanized monoclonal anti-C5 antibody that prevents the activation of the terminal complement pathway. Here, we report the case of a 9-year-old girl with frequent relapsing aHUS due to heterozygous factor H mutation who was initially treated with plasma exchange three times per week with 150% plasma exchange volume. This treatment frequently caused allergic reactions and school absences. Because any reduction in the frequency of plasma exchange immediately induced relapses of the aHUS, treatment with eculizumab, 600 mg every 2 weeks, was started and plasma exchange completely stopped. On this drug regimen the patient showed no evidence of disease activity during a period of more than 24 months. Renal function improved, proteinuria disappeared, the number of antihypertensive medications could be decreased, and the quality of life increased substantially. The inhibition of the terminal complement pathway by eculizumab was also confirmed by renal biopsy, which showed the absence of thrombotic microangiopathy 2 months after the initiation of eculizumab therapy. This case illustrates the long-term favorable outcome of aHUS with eculizumab treatment.