Henoch-Schonlein purpura (HSP) is a systemic disorder characterized by leukocytoclastic vasculitis that can affect multiple organs predominantly the skin, joints, gastrointestinal tract and kidney. Although the specific pathogenesis of HSP is not known, there are several hypotheses. Although the importance of the complement activation in glomerular injury in HSP has been suggested, the complement levels and the blood pressure in those patients are usually normal and massive proteinuria is not common. And pathologic renal changes also have been reported to show a large variety of glomerular changes. However, to our knowledge, a membranoproliferative glomerulo-nephritis (MPGN) is a rare renal clinicopathologic manifestation of HSP. We report a 6-year-old boy with HSP who developed MPGN with hypertension, massive proteinuria, and hypo-complementemia revealed activation of the classical complement pathway, although we could not exclude the possibility of other hypocomplementemic glomerulonephritis including post-streptococcal acute glomerulonephritis.
Blood Pressure ; Child ; Complement Activation ; Complement Pathway, Classical ; Complement System Proteins ; Gastrointestinal Tract ; Glomerulonephritis ; Glomerulonephritis, Membranoproliferative* ; Humans ; Hypertension ; Joints ; Kidney ; Male ; Proteinuria ; Purpura, Schoenlein-Henoch* ; Skin ; Vasculitis

Proteins of the complement system are known to interact with many charged substances. We recently characterized binding of C1q and factor H to immobilized and liposomal anionic phospholipids. Factor H inhibited C1q binding to anionic phospholipids, suggesting a role for factor H in regulating activation of the complement classical pathway by anionic phospholipids. To extend this finding, we examined interactions of C1q and factor H with lipid A, a well-characterized activator of the classical pathway. We report that C1q and factor H both bind to immobilized lipid A, lipid A liposomes and intact Escherichia coli TG1. Factor H competes with C1q for binding to these targets. Furthermore, increasing the factor H: C1q molar ratio in serum diminished C4b fixation, indicating that factor H diminishes classical pathway activation. The recombinant forms of the Cterminal, globular heads of C1q A, B and C chains bound to lipid A and E. coli in a manner qualitatively similar to native C1q, confirming that C1q interacts with these targets via its globular head region. These observations reinforce our proposal that factor H has an additional complement regulatory role of down-regulating classical pathway activation in response to certain targets. This is distinct from its role as an alternative pathway down-regulator. We suggest that under physiological conditions, factor H may serve as a downregulator of bacterially-driven inflammatory responses, thereby fine-tuning and balancing the inflammatory response in infections with Gram-negative bacteria.
Binding, Competitive ; immunology ; Complement Activation ; immunology ; Complement C1q ; chemistry ; immunology ; metabolism ; Complement C4b ; analysis ; Complement Factor H ; chemistry ; immunology ; metabolism ; Complement Pathway, Classical ; immunology ; Escherichia coli ; immunology ; metabolism ; Humans ; Iodine Radioisotopes ; Isotope Labeling ; Lipid A ; immunology ; metabolism ; Liposomes ; immunology ; metabolism ; Protein Binding ; immunology ; Recombinant Proteins ; chemistry ; immunology ; metabolism ; Substrate Specificity

C3 glomerulopathy is a renal disorder involving dysregulation of alternative pathway complement activation. In most instances, a membranoproliferative pattern of glomerular injury with a prevalence of C3 deposition is observed by immunofluorescence microscopy. Dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) are subclasses of C3 glomerulopathy that are distinguishable by electron microscopy. Highly electron-dense transformation of glomerular basement membrane is characteristic of DDD. C3GN should be differentiated from post-infectious glomerulonephritis and other immune complex-mediated glomerulonephritides showing C3 deposits.
Complement Activation ; Complement Pathway, Alternative ; Dichlorodiphenyldichloroethane ; Glomerular Basement Membrane ; Glomerulonephritis ; Glomerulonephritis, Membranoproliferative ; Microscopy, Electron ; Microscopy, Fluorescence ; Pathology ; Prevalence

BACKGROUND: In vitro levels of complement C3 and C4 proteins are sensitive to storage conditions. To avoid in vitro complement activation when testing is delayed, serum should be frozen at -20degrees C within 2 hr of venipuncture. However, this is impractical in routine laboratory work. Therefore, we investigated alterations in C3 and C4 levels in refrigerated specimens over time and derived formulae to estimate initial levels of complement concentrations in delayed testing. METHODS: Ten fresh specimens were measured for C3 and C4 concentrations and were refrigerated at 4degrees C. We measured C3 and C4 levels in refrigerated samples daily for 4 days using an automated nephelometer (Beckman Coulter Inc., USA). RESULTS: C3 and C4 levels were significantly increased over time in refrigerated specimens (P<0.001, P<0.001, respectively). The increments in C3 and C4 levels were described by the equations: C3 (mg/dL)=3.55x+87.18 (r=0.9909), and C4 (mg/dL)=0.72x+22.3 (r=0.9395), where x=the number of days samples were refrigerated before testing. Increases in C3 and C4 concentrations were described on a percentage basis by the equations: DeltaC3 (%)=4.14x+1.07 (r=0.9903), and DeltaC4 (%)=3.57x+2.48 (r=0.9405). CONCLUSIONS: As the measured C3 and C4 concentrations increased by 3.55 mg/dL (4.1%) and 0.72 mg/dL (3.6%) per day in refrigerated specimens, the levels of C3 and C4 should be adjusted in delayed testing. We proposed that the formulae presented be used to back-calculate initial levels of C3 and C4 concentrations.
Complement Activation ; Complement C3* ; Complement C4 ; Complement System Proteins ; Phlebotomy

K/BxN serum can transfer arthritis to normal mice owing to the abundant autoantibodies it contains, which trigger innate inflammatory cascades in joints. Little is known about whether gut-residing microbes affect host susceptibility to autoantibody-mediated arthritis. To address this, we fed C57BL/6 mice with water containing a mixture of antibiotics (ampicillin, vancomycin, neomycin, and metronidazol) for 2 weeks and then injected them with K/BxN serum. Antibiotic treatment significantly reduced the amount of bacterial genomic DNA isolated from fecal samples, in particular a gene encoding 16S ribosomal RNA derived from segmented filamentous bacteria. Arthritic signs, as indicated by the arthritic index and ankle thickness, were significantly attenuated in antibiotic-treated mice compared with untreated controls. Peyer's patches and mesenteric lymph nodes from antibiotic-treated mice contained fewer IL-17-expressing cells than those from untreated mice. Antibiotic treatment reduced serum C3 deposition in vitro via the alternative complement pathway. IL-17-/- congenic C57BL/6 mice were less susceptible to K/BxN serum-transferred arthritis than their wild-type littermates, but were still responsive to treatment with antibiotics. These results suggest that gut-residing microbes, including segmented filamentous bacteria, induce IL-17 production in GALT and complement activation via the alternative complement pathway, which cause the host to be more susceptible to autoantibody-mediated arthritis.
Animals ; Ankle ; Anti-Bacterial Agents ; Arthritis* ; Autoantibodies ; Bacteria ; Complement Activation ; Complement Pathway, Alternative ; DNA ; Genes, vif ; Interleukin-17 ; Joints ; Lymph Nodes ; Mice ; Neomycin ; Peyer's Patches ; RNA, Ribosomal, 16S ; Vancomycin ; Water

The complement system is an innate immune defense machinery comprising components that deploy rapid immune responses and provide efficient protection against foreign invaders and unwanted host elements. The complement system is activated upon recognition of pathogenic microorganisms or altered self-cells by exclusive pattern recognition molecules (PRMs), such as collectins, ficolins and pentraxins. Recent accumulating evidence shows that the different classes of effector PRMs build up a co-operative network and exert synergistic effects on complement activation. In this review, we describe our updated view of the crosstalk between previously unlinked PRMs in complement activation and the potential pathogenic effects during infection and inflammation.
Collectins ; Complement Activation* ; Complement System Proteins* ; Inflammation

Complement Activation ; Humans ; Thrombosis ; immunology

OBJECTIVETo improve our comprehensions to complement activation by biomaterial and lay the foundation for biosafety evaluation of solid biomaterials together with the corresponding blood contacting medical devices.

METHODSAnalyzed new requirements of current standards on complement activation by solid biomaterial as well as the mechanism of complement activation by solid biomaterial and how to select the related standards for inspection.

RESULTS AND CONCLUSIONThe new edition of international standards has enhanced types of blood contacting medical devices which are appropriate to complement activation test. It is badly in need of establishing the corresponding industry standards to regulate these requirements, since there have no uniform and admissive methods for inspection of complement activation by solid biomaterial.

The capacity of tobacco infusions of Korean cigarettes to activate the complement pathway was investigated in vitro by hemolytic assay. Complement activity was studied using samples of normal rabbit serum incubated at 37 degrees C with tobacco infusions. In all mixtures containing tobacco infusion A, B, C, D, E, F, G, H and I at a concentration of 0.1 : 1, total hemolytic complement showed a progressive decrease of 55.92%, 48.62%, 42.89%, 49.12%, 42.26%, 52.26%, 71.96%, 60.90%, and 61.14% respectively, after 60min of incubation. This study suggests that all tobacco infusions of Korean cigarettes are activators of complement.
Complement Activation* ; Complement Hemolytic Activity Assay ; Complement System Proteins* ; Tobacco Products ; Tobacco*

The polysaccharide B3-PS2 was extracted and purified from Herba Scutellariae Barbatae through chromatography of DEAE-cellulose and Sephacryl S-300 column. Average molecular weight of B3-PS2 was about 1,100 kD. It was composed of Glc, Gal and Ara in the ratio of 2.7:2.7:1.0, along with trace of Man, Rha, Fuc and Xyl. B3-PS2 inhibited complement activation on the classic pathways with CH50 value of (0.23 +/- 0.03) mg mL(-1). The targets of B3-PS2 upon the complement system were C1r, C1s, C3 and C4. These results suggested that anti-complementary activity of B3-PS2 was closed to its positive control heparin. It strongly suggested that the polysaccharide B3-PS2 from Herba Scutellariae Barbatae could be a potential candidate in treating those complement-associated diseases.
Complement Activation ; drug effects ; Complement Inactivating Agents ; isolation & purification ; pharmacology ; Drugs, Chinese Herbal ; Polysaccharides ; chemistry ; isolation & purification ; pharmacology ; Scutellaria ; chemistry