Complement alternative pathway acts as a positive feedback amplification of neutrophil activation.

Complement alternative pathway plays an important, but not clearly understood, role in neutrophil-mediated diseases. We here show that neutrophils themselves activate complement when stimulated by cytokines or coagulation-derived factors. In whole blood, tumor necrosis factor/formyl-methionyl-leucyl-phenylalanine or phorbol myristate acetate resulted in C3 fragments binding on neutrophils and monocytes, but not on T cells. Neutrophils, stimulated by tumor necrosis factor, triggered the alternative pathway on their surface in normal and C2-depleted, but not in factor B-depleted serum and on incubation with purified C3, factors B and D. This occurred independently of neutrophil proteases, oxidants, or apoptosis. Neutrophil-secreted properdin was detected on the cell surface and could focus "in situ" the alternative pathway activation. Importantly, complement, in turn, led to further activation of neutrophils, with enhanced CD11b expression and oxidative burst. Complement-induced neutrophil activation involved mostly C5a and possibly C5b-9 complexes, detected on tumor necrosis factor- and serum-activated neutrophils. In conclusion, neutrophil stimulation by cytokines results in an unusual activation of autologous complement by healthy cells. This triggers a new amplification loop in physiologic innate immunity: Neutrophils activate the alternative complement pathway and release C5 fragments, which further amplify neutrophil proinflammatory responses. This mechanism, possibly required for effective host defense, may be relevant to complement involvement in neutrophil-mediated diseases.

Endothelium-neutrophil interactions in ANCA-associated diseases.

The two salient features of ANCA-associated vasculitis (AAV) are the restricted microvessel localization and the mechanism of inflammatory damage, independent of vascular immune deposits. The microvessel localization of the disease is due to the ANCA antigen accessibility, which is restricted to the membrane of neutrophils engaged in ß2-integrin-mediated adhesion, while these antigens are cytoplasmic and inaccessible in resting neutrophils. The inflammatory vascular damage is the consequence of maximal proinflammatory responses of neutrophils, which face cumulative stimulations by TNF-α, ß2-integrin engagement, C5a, and ANCA by the FcγRII receptor. This results in the premature intravascular explosive release by adherent neutrophils of all of their available weapons, normally designed to kill IgG-opsonized bacteria after migration in infected tissues.

Cysteamine therapy delays the progression of nephropathic cystinosis in late adolescents and adults.

Nephropathic cystinosis is a multisystem autosomal recessive disease caused by cystine accumulation, which is usually treated by oral cysteamine. In order to determine long-term effects of this therapy, we enrolled 86 adult patients (mean age 26.7 years) diagnosed with nephropathic cystinosis, 75 of whom received cysteamine. Therapy was initiated at a mean age of 9.9 years with a mean duration of 17.4 years. By last follow-up, 78 patients had end-stage renal disease (mean age 11.1 years), 62 had hypothyroidism (mean age 13.4), 48 developed diabetes (mean age 17.1 years), and 32 had neuromuscular disorders (mean age 23.3 years). Initiating cysteamine therapy before 5 years of age significantly decreased the incidence and delayed the onset of end-stage renal disease, and significantly delayed the onset of hypothyroidism, diabetes, and neuromuscular disorders. The development of diabetes and hypothyroidism was still significantly delayed, however, in patients in whom therapy was initiated after 5 years of age, compared with untreated patients. The life expectancy was significantly improved in cysteamine-treated versus untreated patients. Thus, cysteamine decreases and delays the onset of complications and improves life expectancy in cystinosis. Hence, cysteamine therapy should be introduced as early as possible during childhood and maintained lifelong.

Acquired and genetic complement abnormalities play a critical role in dense deposit disease and other C3 glomerulopathies.

Dense deposit disease and glomerulonephritis with isolated C3 deposits are glomerulopathies characterized by deposits of C3 within or along the glomerular basement membrane. Previous studies found a link between dysregulation of the complement alternative pathway and the pathogenesis of these diseases. We analyzed the role of acquired and genetic complement abnormalities in a cohort of 134 patients, of whom 29 have dense deposit disease, 56 have glomerulonephritis with isolated C3 deposits, and 49 have primary membranoproliferative glomerulonephritis type I, with adult and pediatric onset. A total of 53 patients presented with a low C3 level, and 65 were positive for C3 nephritic factor that was significantly more frequently detected in patients with dense deposit disease than in other histological types. Mutations in CFH and CFI genes were identified in 24 patients associated with a C3 nephritic factor in half the cases. We found evidence for complement alternative pathway dysregulation in 26 patients with membranoproliferative glomerulonephritis type I. The complement factor H Y402H variant was significantly increased in dense deposit disease. We identified one at-risk membrane cofactor protein (MCP) haplotype for glomerulonephritis with isolated C3 deposits and membranoproliferative glomerulonephritis type I. Thus, our results suggest a critical role of fluid-phase alternative pathway dysregulation in the pathogenesis of C3 glomerulopathies as well as in immune complex-mediated glomerular diseases. The localization of the C3 deposits may be under the influence of MCP expression.

Pauci-immune crescentic glomerulonephritis associated with ANCA of IgA class.

Pauci-immune renal vasculitis is associated strongly with antineutrophil cytoplasmic antibodies (ANCAs) of the immunoglobulin G (IgG) class, which are detected in 80% to 90% of affected patients. IgA ANCAs have been reported in association with various conditions, but never in the setting of pauci-immune vasculitis. A 28-year-old man with unexplained polyclonal hyper-IgA1 diagnosed in childhood presented with decreased kidney function, nephrotic syndrome, and microscopic hematuria. Kidney biopsy showed pauci-immune crescentic glomerulonephritis. Serum test results were negative for IgG ANCA by means of both indirect immunofluorescence and enzyme-linked immunosorbent assay techniques. Conversely, indirect immunofluorescence performed using anti-IgA antibody was strongly positive with a cytoplasmic ANCA pattern, and an enzyme-linked immunosorbent assay test had positive results for both antimyeloperoxidase and anti-proteinase 3 IgA. IgA ANCAs were not detected in 2 control serum samples from 1 patient with polyclonal hyper-IgA and 1 patient with monoclonal hyper-IgA. The patient received corticosteroids and 4 weekly perfusions of rituximab (375 mg/m2). After a 6-month follow-up, decreased kidney function and nephrotic syndrome persisted and IgA ANCA titers were unchanged. However, a control kidney biopsy showed a decrease in vasculitis activity. This first case of pauci-immune vasculitis associated with ANCA of the IgA class suggests the potential pathogenetic role of these peculiar antibodies. Additional studies are needed to determine whether IgA ANCAs, which are not routinely screened for, can be detected in patients with pauci-immune vasculitis either alone or in association with IgG ANCA.

The macrophage-derived neutrophil chemotactic factor, MNCF: a lectin with TNF-alpha-like activities on neutrophils.

The macrophage-derived neutrophil chemotactic factor (MNCF) is an alpha-galactoside-binding lectin, known to induce dexamethasone-insensitive neutrophil recruitment. We further characterized MNCF effects on neutrophils and showed that it shares with TNF-alpha the ability to delay apoptosis and to trigger degranulation. MNCF and TNF-alpha effects show similar kinetics and involve Src kinases and MAPKinases dependent pathways. They were, however, clearly distinguished, since the soluble TNF-receptor etanercept prevented TNF but not MNCF effects, while melibiose disaccharide inhibited MNCF but not TNF effects. Absorption of MNCF on detoxi-gel did not alter its properties, precluding an LPS contamination effect. By contrast, galectin-3 required LPS to activate neutrophils. Specific antibodies allowed to further demonstrate that MNCF and galectin-3 are two distinct molecules. Finally, MNCF- and IL-8-induced neutrophil activation differed by their kinetic and sensitivity to pertussis toxin. In conclusion, MNCF is a distinct neutrophil agonist, with pro-inflammatory activities involving its carbohydrate recognition domain.

Primary glomerulonephritis with isolated C3 deposits: a new entity which shares common genetic risk factors with haemolytic uraemic syndrome.

INTRODUCTION: Abnormal control of the complement alternative pathway (CAP) (factor H, factor I and membrane cofactor protein (MCP) deficiencies) is a well established risk factor for the occurrence of haemolytic uraemic syndrome (HUS). In some instances, HUS may be associated with an unusual glomerulonephritis with isolated C3 deposits (glomerulonephritis C3). We determined whether HUS and glomerulonephritis C3 share common genetic susceptibility factors. METHODS: We identified 19 patients with glomerulonephritis C3. We measured levels of circulating complement components, performed assays for the detection of C3 nephritic factor (C3NeF) and screened factor H, factor I and MCP coding genes for the presence of mutations. RESULTS: Patients were divided in two groups based on renal pathology findings: group I (n = 13) had typical features of type I membranoproliferative glomerulonephritis (glomerulonephritis C3 with membranoproliferative glomerulonephritis (MPGN)) and group II (n = 6) was characterised by mesangial and epimembranous C3 deposits in the absence of mesangial proliferation (glomerulonephritis C3 without MPGN). Mutations in complement regulatory genes were detected in 4/6 patients with glomerulonephritis C3 without MPGN (heterozygous mutations in factor H gene (two patients) with low factor H antigenic level in one case, heterozygous mutations in factor I gene (two patients)) and in only 2/13 patients with glomerulonephritis C3 with MPGN (heterozygous mutations in factor H gene (one patient) and double heterozygous mutation in CD 46 gene (one patient)). In contrast, C3NeF was present in 5/13 patients with glomerulonephritis C3 with MPGN and in 2/6 patients with glomerulonephritis C3 without MPGN, one of whom had a factor H mutation. CONCLUSION: HUS and glomerulonephritis C3 without MPGN share common genetic risk factors. Constitutional or acquired dysregulation of the CAP is probably associated with a wide spectrum of diseases, ranging from HUS to glomerulonephritis C3 with MPGN.

Inhibition of matrix metalloproteinase-9 by interferons and TGF-beta1 through distinct signalings accounts for reduced monocyte invasiveness.

Cytokines may provide signals for regulating human monocyte matrix metalloproteinase-9 (MMP-9) activity. In this study, we investigated the roles of interferons (IFN) type I/II and transforming growth factor-beta1 (TGF-beta1) in MMP-9-mediated invasiveness. MMP-9 antibody and inhibitor, IFNs and TGF-beta1 inhibited monocyte transmigration through Matrigel. IFNs and TGF-beta1 downregulated MMP-9 mRNA, protein and activity levels. The inhibitory action of IFNs was associated with the STAT1/IRF-1 pathway since the JAK inhibitor AG490 blocked STAT1 phosphorylation, IRF-1 synthesis and counteracted the blockade of MMP-9 release. TGF-beta1-mediated MMP-9 inhibition appeared STAT1/IRF-1-independent but reversed by the protein tyrosine kinase inhibitor tyrphostin 25. Our data point out the importance of IFNs and TGF-beta1 in the control of monocyte MMP-9-mediated extravasation.

Type III cryoglobulinemia complicated by renal cortical necrosis.

Renal involvement is rare in patients with type III cryoglobulinemia. We report a case of renal cortical necrosis in a patient with type III cryoglobulinemia. Renal function improved partially after treatment with plasma exchange, steroids, and cyclophosphamide. Renal magnetic resonance imaging was a valuable tool in the evaluation of the extent of renal cortical necrosis and improvement in renal vascularization after treatment.

Apoptosis-induced proteinase 3 membrane expression is independent from degranulation.

Proteinase 3 (PR3) and human neutrophil elastase (HNE) are serine proteinases stored in the azurophilic granules of neutrophils. In contrast to HNE, PR3 is the target of antineutrophil cytoplasm antibodies (ANCA) in Wegener's granulomatosis. The mechanisms leading to the membrane expression of PR3 and HNE are still unclear and appear to be critical to understand the pathophysiological role of ANCA. Stably transfected rat basophilic cell lines (RBL) with PR3 or HNE were used to analyze the PR3 and HNE secretion mechanisms and differentiate between them. RBL cells were lacking endogenous PR3 and HNE. They were stably transfected with HNE or PR3 or an inactive mutant of PR3 (PR3S203A). Using the calcium ionophore A23187 as a secretagogue, higher serine proteinase activity was secreted in the supernatant of RBL/HNE than in RBL/PR3. It is interesting that PR3 and PR3/S203A were also expressed at the plasma membrane, thus demonstrating that serine protease activity was not required for plasma membrane expression. In contrast, no expression of plasma membrane HNE could be detected in RBL/HNE. Apoptosis induced by etoposide was evaluated by DNA fragmentation, the presence of cytoplasmic histone-associated DNA fragments, and annexin V labeling. No membrane HNE was detected in RBL/HNE. In contrast, in RBL/PR3 and in RBL/PR3S203A, the membrane expression of PR3 and PR3S203A increased with etoposide concentrations and appeared closely related to annexin V labeling. Our data suggest that membrane PR3 originates from two distinct pools, the granular pool mobilized following degranulation or a plasma membrane pool mobilized upon apoptosis.

SLE and idiopathic nephrotic syndrome: coincidence or not?

BACKGROUND: The association of systemic lupus erythematosus (SLE) with minimal change disease (MCD) and/or focal and segmental glomerulosclerosis (FSGS) has been described in isolated case reports. The relevance of this association is still debated. METHODS: We performed a retrospective and descriptive study of 11 patients with SLE who experienced idiopathic nephrotic syndrome (iNS) in an effort to determine the relevance of this unusual combination. RESULTS: All patients fulfilled at least four criteria (renal abnormalities excluded) of the American Rheumatologic Association for the diagnosis of SLE, and all had severe nephrotic syndrome (mean proteinuria, 9.23 +/- 6 g of protein/24 h; serum albumin concentration, 1.48 +/- 0.6 g/dL). None had a past medical history of lupus nephritis or a cause for secondary FSGS. Renal histological examination showed MCD (4 patients) or FSGS (7 patients) without mesangial proliferation. Immunofluorescence was negative in 8 patients. In 3 patients, immune deposits (immunoglobulin G, immunoglobulin M, C3, and C1q) were present, but confined to the mesangium without glomerular changes on light microscopy. The abrupt onset of nephrotic syndrome coincided with the appearance of SLE in 6 patients (group 1) and recurrence of SLE in 3 patients (group 2). Two patients in group 1 experienced SLE recurrence with concomitant relapse of nephrotic syndrome. In only 2 patients (group 3) were the two diseases independent. CONCLUSION: These results suggest that a relevant association exists between both diseases, and SLE could be a precipitating factor for iNS.

Renal involvement in monoclonal (type I) cryoglobulinemia: two cases associated with IgG3 kappa cryoglobulin.

Renal involvement has been described rarely in monoclonal (type I) cryoglobulinemia, although this complication is frequent among patients with mixed (type II or III) cryoglobulin. We report two patients with glomerulonephritis and monoclonal IgGkappa cryoglobulin. Both patients presented with nephrotic syndrome, microscopic hematuria, and impaired renal function. Hepatitis C serology was negative, bone marrow aspiration was normal, and the renal biopsy specimen showed membranoproliferative glomerulonephritis with glomerular subendothelial deposits of monoclonal IgGkappa. In both cases, circulating cryoglobulin and monotypic tissue deposits were found to be IgG3kappa, suggesting that this isotype may have a particular propensity to cause this type of membranoproliferative glomerulonephritis. Although 18 cases of type I cryoglobulinemia with biopsy-proven glomerulonephritis have been reported to date, this is the first characterization of immunoglobulin heavy-chain isotype in this disease.

Steroid-sensitive nephrotic syndrome: from childhood to adulthood.

BACKGROUND: The clinical presentation, treatment, and outcome of steroid-sensitive nephrotic syndrome (SSNS) during childhood have been extensively studied. Conversely, few data regarding the outcome in adulthood of childhood SSNS have been published previously. We undertook to conduct a retrospective study of the outcome in adulthood of a large cohort of patients diagnosed with an SSNS during childhood. METHODS: We identified all children born between 1970 and 1975 who had been admitted to our institution for an SSNS. Data regarding the outcome in adulthood of these patients were obtained through mailed questionnaires or phone calls to patients and/or their parents or through attending physicians. RESULTS: One hundred seventeen patients were identified. Data regarding the outcome of SSNS in adulthood were available for 102 patients (87.2%). Forty-three patients (42.2%) experienced at least one relapse of nephrotic syndrome in adulthood. By univariate analysis, young age at onset (<6 years) and more severe disease in childhood, indicated by a greater number of relapses (12.9 for adulthood relapsers versus 5.4 for adulthood nonrelapsers; P < 0.0001) and more frequent use of immunosuppressors (74.4% versus 31.6%; P < 0.0001) or cyclosporine (42.9% versus 7.3%; P < 0.0001) were predictive of the occurrence of SSNS relapse in adulthood. Conversely, relapse rate in the first 6 months of disease was not predictive of further relapses in adulthood. By multivariate analysis, only number of relapses during childhood was predictive of adulthood relapses (P < 0.0058). Long-term side effects of steroids were found in 44.2% of adulthood relapsers; the most frequent were osteoporosis and excess weight. CONCLUSION: The incidence of childhood SSNS relapses in adulthood was relatively high in our study. Further studies are required to assess long-term complications in adults with relapses and a history of prolonged steroid and immunosuppressor use.

The expanding spectrum of renal diseases associated with antiphospholipid syndrome.

BACKGROUND: The association of thrombotic events and/or pregnancy complications with circulating antiphospholipid antibodies defines antiphospholipid syndrome (APS). In previous reports, renal involvement in APS consisted mainly of thrombotic vascular complications involving large vessels or intrarenal small-sized vessels (APS nephropathy). We report 9 cases of glomerulonephritis associated with APS. These cases are characterized by predominant pathological features distinct from vascular APS nephropathy. METHODS: We reviewed consecutive renal biopsies examined in 2 French university hospitals between 1980 and 2002 and identified renal biopsies performed in patients with primary APS. RESULTS: We identified 29 biopsies performed in patients with APS. Twenty biopsies showed characteristic features of APS nephropathy. In 9 cases, predominant pathological features distinct from vascular APS nephropathy were noted: membranous nephropathy (3 cases), minimal change disease/focal segmental glomerulosclerosis (3 cases), mesangial C3 nephropathy (2 cases), and pauci-immune crescentic glomerulonephritis (1 case). In 7 cases, the presentation of renal symptoms was subacute or chronic. Two patients experienced episodes of acute renal failure. At referral, median creatinine clearance was 50 mL/min (0.83 mL/s) (range, 18 to 117 mL/min [0.30 to 1.95 mL/s]). Proteinuria was noted in all cases (range, 1.5 to 15 g/d), with nephrotic syndrome in 4 cases. Lupus anticoagulant was present in all cases, and anticardiolipin antibodies, in 8 cases. Anti-DNA antibodies repeatedly were negative in all cases. Treatment consisted of antihypertensive therapy (6 cases), anticoagulant drugs (5 cases), steroids (4 cases), and antiplatelet drugs (3 cases). At last follow-up, renal function remained stable in 7 patients. Of 2 patients presenting with acute renal failure, 1 patient recovered normal renal function, whereas the other patient progressed to end-stage renal failure. CONCLUSION: The cases reported here represent a new aspect of the expanding spectrum of renal diseases encountered in association with APS.

[Secondary glomerular nephropathies]. / Glomérulopathies secondaires.

Secondary glomerular lesions are associated with various diseases; diabetes, systemic lupus erythematosus, primary cryoglobulinaemia, cryoglobulinemia and membranoproliferative glomerulonephritis secondary to hepatitis C virus (HCV), ANCA associated vasculitis and their forms limited to kidney (necrotic and crescentic GN), Goodpasture syndrome, HIV associated nephropathies, AL amyloidosis, AA amyloidosis (secondary amyloidosis), GN with non-amyloid organised deposits.

C3 glomerulopathy.

C3 glomerulopathy is a recent disease classification comprising several rare types of glomerulonephritis, including dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). The most common histological feature in these diseases is the presence of glomerular deposition of C3 within the mesangium and along the glomerular basement membrane (GBM) in the subendothelial area or within the GBM. The key role of complement alternative pathway (AP) in these disorders has been recently shown with the identification of acquired or genetic abnormalities. Low serum C3 level but normal C4 is a common finding. The acquired AP dysregulation in DDD and C3GN may be first induced by C3 nephritic factor (C3NeF). C3NeF activity is found in approximately 80% of patients with DDD and in 45% of patients with C3GN. The correlation with the complement is further supported by the detection of homozygous or heterozygous mutations in the regulatory complement proteins factor H (CFH), factor I (CFI), or C3. The genetic background of the patients may also influence the disease manifestation since common genetic variants including single nucleotide polymorphisms in the CFH, C3 and CFHR5 genes are associated with DDD and one at-risk MCP haplotype have been found to be significantly increased in C3GN. C3 glomerulopathies can present over a broad age range. DDD is more often diagnosed in children and age at diagnosis is significantly higher for patients with C3GN. Presenting features comprise any of proteinuria, hematuria, hypertension and renal failure. These glomerulonephritides are associated with chronic deterioration of renal function, leading to ESRD within 10 years of the diagnosis in 36-50% of patients. Outcomes of renal transplantation are characterized by histological recurrence which may contribute to increased rates of allograft failure. Administration of recombinant FH if it becomes available or replacement of FH via plasma exchange may be efficacious in the cases of FH deficiency. However, therapeutic inhibition of complement C3 and C5 is the main perspective.

M-ficolin and leukosialin (CD43): new partners in neutrophil adhesion.

M-ficolin specificity for sialylated ligands prompted us to investigate its interactions with the main membrane sialoprotein of human neutrophils, CD43. rM-ficolin bound CD43 and prevented the access of anti-CD43 mAb. Moreover, rM-ficolin reacted exclusively with CD43 on Western blots of neutrophil lysate. We confirmed that M-ficolin is secreted by fMLP-activated neutrophils, and this endogenous M-ficolin also binds to CD43 and competes with anti-CD43 mAb. Anti-CD43 antibody cross-linking or fMLP resulted in M-ficolin and CD43 colocalization on polarized neutrophils. The binding of rM-ficolin to resting neutrophils induced cell polarization, adhesion, and homotypic aggregation as anti-CD43 mAb. The M-ficolin Y271F mutant, unable to bind sialic acid, neither reacted with neutrophils nor modulated their functions. Finally, rM-ficolin activated the lectin complement pathway on neutrophils. These results emphasize a new function of M-ficolin, different from ficolin pathogen recognition, i.e., a participation to neutrophil adhesion potentially important in early inflammation, as nanomolar agonist concentrations are sufficient to mobilize M-ficolin to the neutrophil surface. This multivalent lectin could then endow the antiadhesive CD43, essentially designed to prevent leukocyte aggregation in the blood flow, with new adhesive properties and explain, at least in part, dual-adhesive/antiadhesive roles of CD43 in neutrophil recruitment.

Heterogeneous pattern of renal disease associated with homozygous factor H deficiency.

Membranoproliferative glomerulonephritis type II is a rare renal disease, associated with uncontrolled activation of the complement alternative pathway because of C3 nephritic factor. Abnormalities in factor H have been rarely described in patients with membranoproliferative glomerulonephritis type II. We report the clinical history, molecular defect, and histologic description of 3 patients with factor H deficiency and various types of membranoproliferative glomerulonephritis. The 3 patients presented with severely decreased C3. Circulating factor H was undetectable. Complete factor H deficiency (CFH) was due to homozygous complement factor H mutations in short consesus repeat (SCR) 7, 10, and 11. Age at onset was 1 (patient 1), 17 (patient 2), and 33 years (patient 3). Symptoms at diagnosis included proteinuria of 0.5, 2.4, and 11 g/d, respectively, microhematuria, and normal renal function in all cases. The estimated glomerular filtration rate at last follow-up was 25, 43, and 112 mL/min per 1.73 m(2), at ages of 29, 24, and 37 years, respectively. Renal biopsies disclosed a membranoproliferative glomerulonephritis type II with atypical discontinuous dense deposits in patient 1; a membranoproliferative glomerulonephritis type I with immunoglobin G (IgG), C1q, and abundant C3 deposits in patient 2; and a membranoproliferative glomerulonephritis with isolated C3 deposits without dense deposits in patient 3. This report of factor H-deficient patients emphasizes the diversity of the histologic lesions associated with factor H deficiencies and the role of the alternative pathway in several subtypes of membranoproliferative glomerulonephritis.