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IgA nephropathy (IgAN) is common chronic glomerulonephritis with variable prognosis, ranging from minor urinary abnormalities to end-stage renal disease. The revised Oxford classification of IgAN explains that cellular/fibrocellular crescents are associated with poor renal prognosis, proposing an extension to the MEST-C score. C3 immunofluorescent staining follows a distribution similar to IgA staining. Therefore, complement activation was reported to play a pivotal role in IgAN pathogenesis. This study included 132 IgAN patients diagnosed by renal biopsies. The clinical parameters at the time of the biopsies were obtained from patient data records. We classified the patients into C ≥ 1 and C0 groups, and compared clinical, light microscopic, and immunofluorescent features. In the C ≥ 1 group, 2 (1.5%) and 31 (23.5%) patients were assigned to C2 and C1, respectively. The remaining 99 patients (75%) were classified as C0. The C ≥ 1 group had lower average age and rate of hypertension, and higher score of urinary occult blood and E score. The C ≥ 1 group had significantly higher average immunofluorescence scores for IgA, C5b-9, mannose-associated serine protease (MASP) 1/3, MASP2, properdin, factor B, and kappa. The steroid use rate was significantly higher in the C ≥ 1 group. During the follow-up period of 2.90 years on average, the rate of renal dysfunction was not significantly different between groups. Crescent formation in IgAN was associated with activation of the lectin and alternative pathways. The C ≥ 1 group had significantly increased use of steroids, which probably caused comparable renal function during the follow-up period.

The complement system (CS) is an integral part of innate immunity and can be activated via three different pathways. The alternative pathway (AP) has a central role in the function of the CS. The AP of complement system is implicated in several human disease pathologies. In the absence of triggers, the AP exists in a time-invariant resting state (physiological steady state). It is capable of rapid, potent and transient activation response upon challenge with a trigger. Previous models of AP have focused on the activation response. In order to understand the molecular machinery necessary for AP activation and regulation of a physiological steady state, we built parsimonious AP models using experimentally supported kinetic parameters. The models further allowed us to test quantitative roles played by negative and positive regulators of the pathway in order to test hypotheses regarding their mechanisms of action, thus providing more insight into the complex regulation of AP.

Chronic kidney disease affects millions of people around the globe and many patients rely on hemodialysis (HD) to survive. HD is associated with undesired life-threatening side effects that are linked to membrane biocompatibility and clinical operating conditions. The present study develops a mathematical model to predict the inflammatory biomarkers released in HD patients based on membrane morphology, chemistry, and interaction affinity. Based on the morphological characteristics of two clinical-grade HD membrane modules (CTA and PAES-PVP) commonly used in Canadian hospitals, a molecular docking study, and the release of inflammatory cytokines during HD and in vitro incubation experiments, we develop five sets of equations that describe the concentration of eight biomarkers (serpin/antithrombin-III, properdin, C5a, 1L-1α, 1L-1β, C5b-9, IL6, vWF). The equations developed are functions of membrane properties (pore size, roughness, chemical composition, affinity to fibrinogen, and surface charge) and HD operating conditions (blood flow rate, Qb, and treatment time, t). We expand our model based on available clinical data and increase its range of applicability in terms of flow rate and treatment time. We also modify the original equations to expand their range of applicability in terms of membrane materials, allowing the prediction and validation of the inflammatory response of several clinical and synthesized membrane materials. Our affinity-based model solely relies on theoretical values of molecular docking, which can significantly reduce the experimental load related to the development of more biocompatible materials. Our model predictions agree with experimental clinical data and can guide the development of novel materials and support evidence-based membrane synthesis of HD membranes, reducing the need for trial-and-error approaches.

In the search for improved stool biomarkers for inflammatory bowel disease (IBD), an aptamer-based screen of 1129 stool proteins was conducted using stool samples from an IBD cohort. Here we report that of the 20 proteins subsequently validated by ELISA, stool Ferritin, Fibrinogen, Haptoglobin, Hemoglobin, Lipocalin-2, MMP-12, MMP-9, Myeloperoxidase, PGRP-S, Properdin, Resistin, Serpin A4, and TIMP-1 are significantly elevated in both ulcerative colitis (UC) and Crohn’s disease (CD) compared to controls. When tested in a longitudinal cohort of 50 UC patients at 4 time-points, fecal Fibrinogen, MMP-8, PGRP-S, and TIMP-2 show the strongest positive correlation with concurrent PUCAI and PGA scores and are superior to fecal calprotectin. Unlike fecal calprotectin, baseline stool Fibrinogen, MMP-12, PGRP-S, TIMP-1, and TIMP-2 can predict clinical remission at Week-4. Here we show that stool proteins identified using the comprehensive aptamer-based screen are superior to fecal calprotectin alone in disease monitoring and prediction in IBD., Stool biomarkers hold promise for monitoring disease activity and predicting clinical course in inflammatory bowel disease (IBD) as they originate from the inflamed tissue. Here the authors report an aptamer-based proteomic screen, and discover several stool proteins that predict remission at four weeks.

Abuse of alcohol and tobacco could exacerbate HIV pathogenesis by transferring materials through exosomes (small nanovesicles). Exosomes present a stable and accessible source of information concerning the health and/or disease status of patients, which can provide diagnostic and prognostic biomarkers for myriad conditions. Therefore, we aimed to study the specific exosomal proteins that are altered in both HIV-infected subjects and alcohol/tobacco users. Exosomes were isolated from plasma of the following subjects: a) HIV-negative subjects (healthy), b) HIV-positive subjects (HIV), c) HIV-negative alcohol drinkers (drinkers), d) HIV-negative tobacco smokers (smokers), e) HIV-positive drinkers (HIV + drinkers), and f) HIV-positive smokers (HIV + smokers). Quantitative proteomic profiling was then performed from these exosomes. Sixteen proteins were significantly altered in the HIV group, ten in drinkers, four in HIV + drinkers, and fifteen in smokers compared to healthy subjects. Only one protein, fibulin-1 (FBLN1), was significantly altered in HIV + smokers. Interestingly, hemopexin was not significantly altered in drinkers or HIV patients but was significantly altered in HIV + drinkers. Further, our study is the first to show properdin expression in plasma exosomes, which was decreased in HIV + smokers and HIV + drinkers compared to HIV patients. The present findings suggest that hemopexin and properdin show potential as markers for physiological effects that may arise in HIV-infected individuals who abuse alcohol and tobacco. Graphical abstract This study presents a proteomic analysis of plasma-derived exosomes from HIV-infected alcohol drinkers and smokers. Among the proteins altered due to drug-abuse, hemopexin and properdin were of highest significance. These proteins can be potential biomarkers for co-morbid conditions associated with drug abuse in HIV-patients.

Two large-scale Florida manatee (Trichechus manatus latirostris) mortality episodes were reported on separate coasts of Florida in 2013. The east coast mortality episode was associated with an unknown etiology in the Indian River Lagoon (IRL). The west coast mortality episode was attributed to a persistent Karenia brevis algal bloom or ‘red tide’ centered in Southwest Florida. Manatees from the IRL also had signs of cold stress. To investigate these two mortality episodes, two proteomic experiments were performed, using two-dimensional difference in gel electrophoresis (2D-DIGE) and isobaric tags for relative and absolute quantification (iTRAQ) LC–MS/MS. Manatees from the IRL displayed increased levels of several proteins in their serum samples compared to controls, including kininogen-1 isoform 1, alpha-1-microglobulin/bikunen precursor, histidine-rich glycoprotein, properdin, and complement C4-A isoform 1. In the red tide group, the following proteins were increased: ceruloplasmin, pyruvate kinase isozymes M1/M2 isoform 3, angiotensinogen, complement C4-A isoform 1, and complement C3. These proteins are associated with acute-phase response, amyloid formation and accumulation, copper and iron homeostasis, the complement cascade pathway, and other important cellular functions. The increased level of complement C4 protein observed in the red tide group was confirmed through the use of Western Blot.

Properdin is known as the only positive regulator of the complement system. Properdin promotes the activity of this defense system by stabilizing its key enzymatic complexes: the complement alternative pathway (AP) convertases. Besides, some studies have indicated a role for properdin as an initiator of complement activity. Though the AP is a powerful activation route of the complement system, it is also involved in a wide variety of autoimmune and inflammatory diseases, many of which affect the kidneys. The role of properdin in regulating complement in health and disease has not received as much appraisal as the many negative AP regulators, such as factor H. Historically, properdin deficiency has been strongly associated with an increased risk for meningococcal disease. Yet only recently had studies begun to link properdin to other complement-related diseases, including renal diseases. In the light of the upcoming complement-inhibiting therapies, it is interesting whether properdin can be a therapeutic target to attenuate AP-mediated injury. A full understanding of the basic concepts of properdin biology is therefore needed. Here, we first provide an overview of the function of properdin in health and disease. Then, we explore its potential as a therapeutic target for the AP-associated renal diseases C3 glomerulopathy, atypical hemolytic uremic syndrome, and proteinuria-induced tubulointerstitial injury. Considering current knowledge, properdin-inhibiting therapy seems promising in certain cases. However, knowing the complexity of properdin's role in renal pathologies in vivo, further research is required to clarify the exact potential of properdin-targeted therapy in complement-mediated renal diseases. ispartof: PEDIATRIC NEPHROLOGY vol:34 issue:8 pages:1349-1367 ispartof: location:Germany status: published

This review is not intended to cover in detail all aspects of the discovery and evolution of our understanding of the "alternative pathway" of complement activation, there are many excellent reviews that do this (see Fearon (CRC Crit Rev Immunol 1:1-32, 1979), Pangburn and Müller-Eberhard (Springer Semin Immunopathol 7:163-192, 1984)), but instead to give sufficient background for current concepts to be put in context. The prevailing textbook view, of components having a primary role as an alternative "pathway" for C3 activation, is challenged, with an argument developed for the primary role of the system being that of providing a surface-dependent amplification loop for both C3 and C5 activation. Whatever the mechanism by which the initial C3b molecule is generated, deposition onto a surface has the potential to target that surface for elimination. Elimination or escape from initial targeting is determined by a sophisticated and highly regulated amplification loop for C3 activation. This viewpoint of the system is then briefly developed to provide a context for therapeutic treatment of disease caused, at least in part, by dysregulated amplification of C3 activation, and to highlight some of the challenges that such therapies will face and need to address.

Background Complement activation plays a substantial role in the pathogenesis of primary membranous nephropathy (pMN). C5b-9, C3c, MBL, and factor B have been documented in the subepithelial immune deposits. However, the changing of complement activation products in circulation and urine is not clear. Methods We measured the circulating and urinary levels of C1q, MBL, C4d, Bb, properdin, C3a, C5a, and sC5b-9, in 134 patients with biopsy-proven pMN, by enzyme-linked immunosorbent assay. All the plasma values were corrected by eGFR and all the urinary values were corrected by urinary creatinine and urinary protein excretion. Anti-PLA2R antibodies were measured in all patients. Results The plasma complement activation products were elevated both in the patients with and without anti-PLA2R antibodies. C3a levels were remarkably increased in the circulation and urine, much higher than the elevated levels of C5a. C5b-9 was in normal range in plasma, but significantly higher in urine. The urinary C5a had a positive correlation with anti-PLA2R antibody levels and urinary protein. The plasma level of C4d was elevated, but C1q and MBL were comparable to healthy controls. Positive correlations were observed between plasma C4d/MBL and urinary protein, only in the patients with positive anti-PLA2R antibodies but not in those without. The plasma level of Bb was elevated and had positive correlation with urinary protein only in the patients without anti-PLA2R antibodies. Conclusion Complement activation products were remarkable increased in pMN and may serve as sensitive biomarkers of disease activity. The complement may be activated through lectin pathway with the existence of anti-PLA2R antibodies, while through alternative pathway in the absence of antibody.

Dense deposit disease (DDD) is a rare glomerular disease caused by an uncontrolled activation of the alternative complement pathway leading to end-stage renal disease in 50 % of patients. As such, DDD has been classified within the spectrum of complement component 3 (C3) glomerulopathies due to its pathogenesis from alternative pathway dysregulation. Conventional immunosuppressive therapies have no proven effectiveness. Eculizumab, a terminal complement inhibitor, has been reported to mitigate disease in some cases. We report on the efficacy of eculizumab in a pediatric patient who failed to respond to cyclophosphamide, corticosteroids, and plasma exchange. Complement biomarker profiling was remarkable for low serum C3, low properdin, and elevated soluble C5b-9. Consistent with these findings, the alternative pathway functional assay was abnormally low, indicative of alternative pathway activity, although neither C3-nephritic factors nor Factor H autoantibodies were detected. Eculizumab therapy was associated with significant improvement in proteinuria and renal function allowing discontinuation of hemodialysis (HD). Repeat C3 and soluble C5b-9 levels normalized, showing that terminal complement pathway activity was successfully blocked while the patient was receiving eculizumab therapy. Repeat testing for alternative pathway activation allowed for a successful decrease in eculizumab dosing. The case reported here demonstrates the successful recovery of renal function in a pediatric patient on HD following the use of eculizumab.

Thrombospondins (TSPs) are a family of five secreted multimeric matricellular proteins that share homology in the type II and III repeats and carboxy-terminal region. Type I repeats, also known as properdin or thrombospondin repeats (TSRs), are found in TSP1/2, but not TSP3-5. A variety of other secreted proteins contain TSRs, including the novel extracellular molecules, R-spondins. TSP family and many TSR-containing proteins, including R-spondins, are highly expressed in skeletal tissues during development and postnatal. TSP2 regulates the osteoblast lineage, influencing bone mass and geometry, as well as response to fracture healing, ovariectomy, and mechanical loading. Compound knockout mice of TSPs have revealed important mechanistic insights. TSP1/2 knockout mice have craniofacial dysmorphism, and TSP1/3/5 compound knockout mice display growth plate abnormalities. R-spondins promote osteoblast differentiation and R-spondin-2 deficiency results in skeletal developmental defects. Overall, TSP and other TSR molecules influence multiple aspects of bone development and remodeling.

Objective: Little is known about the role of local production of complement components by dendritic cells (DCs) during the generation of specifi c immune responses. In this study, we demonstrate that human DCs are an extra- hepatic source of several soluble complement proteins. Methods: Reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot were used to evaluate the expres- sion and production of several complement proteins. Results: We show that DCs produce C3, C5, C9, Factor (F)I, FH, FB, FD and properdin at levels similar to macrophages. Treatment of DCs with lipopolysaccharide (LPS) promoted an increase in the expression of C3 and FI mRNAs and a decrease in C5 mRNA, while C9, FH, FB, FD and properdin mRNA levels were not affected. Treatment with interleukin (IL) -1 or dexamethasone induced a modest increase in C3 mRNA levels and did not affect the expression of other com- plement components. Conclusion: DCs are a source of complement proteins whose synthesis may be regulated in response to different infl ammatory stimuli.

Properdin type I deficiency is characterised by complete absence of extracellular properdin, a positive regulator of the alternative pathway of complement activation. Properdin deficiency is associated with increased susceptibility to severe meningococcal disease. We have identified the genetic defect in 10 Dutch families. Six different mutations and one sequence polymorphism in the properdin gene were found. All amino acid substitutions were limited to conserved amino acids in exons 7 and 8 in contrast to the premature stops that were found in other exons. The missense mutations may alter the protein conformation in such a way that properdin will not be secreted and therefore catabolised intracellularly. The decreased properdin levels found in some healthy females carrying one mutated properdin gene were studied for X-inactivation. Most carriers with extreme low or high properdin levels showed preferential X-inactivation for the normal or mutated X chromosome, respectively. We observed some exceptions, suggesting additional regulation of properdin excretion apart from X-inactivation.

Chronic deficiencies in the complement pathway proteins are associated with an increased risk of meningococcal disease. Such deficiencies are caused by primary congenital immunodeficiency of a complement protein, properdin or mannose binding lectin, or are secondary to consumption of complement by systemic lupus erythematosus (SLE) or membranoproliferative glomerulonephritis (MPGN). Whatever the cause, the complement deficiency is always chronic. Here we report a case of meningococcal disease (MCD) in a child with a transient complement deficiency (CD), caused by post-streptococcal glomerulonephritis (PSGN).

Three properdin deficiency phenotypes have been reported--complete deficiency (type I), incomplete deficiency (type II), and dysfunction of properdin protein (type III)--all associated with increased susceptibility to meningococcal disease. Expression of properdin by monocytes was examined in type I deficiency and in two unrelated cases with type II deficiency, one from a Swedish and one from a Danish family. The properdin gene in the Danish family contained a point mutation in exon 8 causing a Gln316-->Arg substitution, distinct from a point mutation in exon 4 previously found in the Swedish family. Both genes coded for physicochemically abnormal properdin molecules with changed hydrophilicity. Monocytes from all the properdin-deficient individuals produced properdin mRNA in a normal fashion. In type I deficiency no intracellular or secreted properdin was found, indicating rapid intracellular degradation. Monocytes from the males with type II deficiency expressed and secreted properdin normally. Properdin in sera with type II deficiency showed abnormal oligomerization with a relative decrease in properdin trimers and tetramers. Our findings suggest that the low concentration of circulating properdin in type II deficiency is caused by increased extracellular catabolism. Analysis of properdin expression by monocytes in a female carrier in the family with properdin deficiency type I provided direct evidence of lyonization at the cellular level.

Ten patients with Henoch-Schöenlein purpura (HSP) were selected for study because their early renal biopsies showed focal and segmental hypercellularity, with IgA present only in deposits at the periphery of the lobules. Mesangial deposits of IgA were absent. All had laboratory evidence of nephrotic syndrome and/or renal compromise. The glomerular hypercellularity was largely the result of the infiltration of monocytes whose cytoplasm often contained tubular lysosomes and wrapping lysosomal membranes, evidence of monocyte activation. Mean levels of C3 were normal but those of C4 and properdin significantly depressed. This complement profile, as well as a glomerular monocytic infiltrate, are also seen in essential cryoglobulinemia in the adult. Of follow-up biopsies in six patients, the glomeruli were normal in three, with no IgA deposition. In the other three, mesangial deposits of IgA typical of HSP were present. The initial focal-segmental glomerulitis of these patients appeared to be the benign first phase of a disease which had the potential to culminate in mesangial IgA deposition. Patients like the three who escaped mesangial IgA would be among those responsible for the observed dissociation between severity of the initial illness and ultimate prognosis.

p24 antigen (p24 Ag) is usually not found in patients in the asymptomatic phase of HIV infection, mainly because it is bound to anti-p24 antibodies (p24 Ab), with which it forms immune complexes. Nine asymptomatic patients positive for HIV-1 antibodies (stage II CDC criteria) treated with r alpha-interferon were followed (7.5 +/- 0.5 months), and a basal and final sample were tested for p24 Ag immune complexes (p24 Ag-IC), free p24 Ag, p24 Ab, CD4 count, beta 2-microglobulin, properdin B factor, and C3 and C4 complement fractions. p24 Ag-IC was detected in 55.5% of the samples, whereas free p24 Ag was detected in 5.5%. The finding of no change or an increase in p24 Ag-IC serum levels may be considered a prognostic marker. We believe that p24 Ab cannot be used as a prognostic marker unless p24 Ag-IC detection is simultaneously evaluated.

Background Glomerular damage in IgA nephropathy (IgAN) is mediated by complement activation via the alternative and lectin pathways. Therefore, we focused on molecules stabilizing and regulating the alternative pathway C3 convertase in urine which might be associated with IgAN pathogenesis. Methods Membrane attack complex (MAC), properdin (P), factor H (fH) and Complement receptor type 1 (CR1) were quantified in urine samples from 71 patients with IgAN and 72 healthy controls. Glomerular deposition of C5, fH and P was assessed using an immunofluorescence technique and correlated with histological severity of IgAN and clinical parameters. Fibrotic changes and glomerular sclerosis were evaluated in renal biopsy specimens. Results Immunofluorescence studies revealed glomerular depositions of C5, fH and P in patients with IgAN. Urinary MAC, fH and P levels in IgAN patients were significantly higher than those in healthy controls (p < 0.001), but CR1 was significantly lower than that in healthy controls (p < 0.001). Urinary MAC and fH levels were positively correlated with serum creatinine (sCr), urinary N-acetyl-β-D-glucosaminidase (u-NAG), urinary β2 microglobulin (u-Bm), urinary protein (p < 0.001), interstitial fibrosis (MAC: p < 0.01, fH: p < 0.05) and the percentage of global glomerular sclerosis (p < 0.01). Urinary P was positively correlated with u-NAG, u-Bm, and urinary protein (p < 0.01). Conclusions Complement activation occurs in the urinary space in IgAN and the measurement of levels of MAC and fH in the urine could be a useful indicator of renal injury in patients with IgAN.

Serum concentrations of the various complement components including the classical and the alternative pathways were determined in 58 control healthy subjects and 80 patients with systemic sclerosis (SSC). The mean concentrations of C1q, C2, C5, C6, C7, C9, and factor B were significantly increased in the SSC patients in comparison to controls, while the increases were not significant for C3 and C8. C4 was an exception in that the mean levels were found to be decreased with 18 patients having levels

Properdin plays a key role in the alternative pathway by stabilizing the C3 convertase. This review chronicles the evolution of our knowledge of the structure and function of properdin over the 40 years since its discovery. The story begins with the first description of properdin and the controversy that ensued over its existence. Then, this review describes: the rediscovery and acceptance of properdin and the alternative pathway as important components of natural immunity; properdin structure and molecular sequence; speculations on the significance of sequence similarities to thrombospondin and other proteins, and properdin biosynthesis. Finally, this review characterizes properdin deficiency. Properdin does indeed appear to play an important role in homeostasis.

PBC is a chronic progressive liver disease of unknown etiology. Several abnormalities found in PBC support the hypothesis that it may be considered an autoimmune disease. Despite the complex and interesting relationship that exists between autoimmune disorders and the complement system, very few reports on the level of the serum complement component in PBC have been published, and most of these comprised only a few patients or analyzed only a scant number of the complement components. In the present study, sera of 73 PBC patients were analyzed for the levels of 10 complement components. It was found that the levels of most of the serum complement components, including C1q, C2, C3, C5, C7, properdin and factor B were significantly elevated in patients with PBC in comparison to healthy controls. The level of C4 was slightly lower than that of the normal controls (p = 0.019), while the levels of C6 and C8 were within the normal range. The number of PBC patients with serum levels of C4 and C660% of normal pooled serum was higher than in the respective control groups (6/69 compared with 0/26 and 4/71 compared with 0/27, respectively). However, the difference was not statistically significant. Thus, our study shows alterations in the levels of most complement components in PBC, the reasons for which are discussed.

In a murine model of antiphospholipid antibody (aPL)-induced pregnancy loss, we have demonstrated that activation of complement, specifically C5a–C5a receptor interactions, leads to fetal loss and growth restriction. Yet, the effectors of tissue injury, the role of individual complement activation pathways and the precise targets for treatment remain unknown. Because C5a recruits and activates polymorphonuclear leukocytes (PMN) and because PMN infiltration is evident at sites of fetal resorption, we considered the possibility that PMN are critical cellular effectors of fetal damage. To assess the effects of aPL antibodies in mice depleted of granulocytes, we treated pregnant mice with anti-mouse Ly-6G (α-Gr) or control murine IgG2K prior to administration of human IgG containing aPL (aPL-IgG). In the absence of granulocytes, mice did not develop aPL-induced pregnancy complications. The frequency of fetal resorptions was similar to that of mice treated with IgG from healthy controls (NH-IgG), while treatment with control IgG2bK was not protective (% fetal resorption, aPL-IgG + α-Gr, 8.5 ± 1.5%; NH-IgG, 10 ± 2; aPL + IgG2bK, 39 ± 5%*; fetal weight (mg), aPL + α-Gr, 352 ± 48; NH-IgG, 370 ± 56; aPL + IgG2bK, 187 ± 28*; * aPL vs NH-IgG, P < 0.01). Immunohistochemical analysis of decidual tissues showed that, in the absence of neutrophil infiltration, either as a consequence of neutrophil depletion or due to blockade of the C5a–C5aR interaction, there was limited C3 deposition coincident with improved pregnancy outcomes. It has been suggested that neutrophils promote complement activation by secreting C3 and/or properdin at sites of inflammation, and thereby amplify complement activation via the alternative pathway. To examine the contribution of the alternative pathway to aPL-induced pregnancy loss, we performed studies in mice deficient in factor B (fB). In the absence of fB, mice were protected from aPL-induced fetal resorption and growth restriction (% fetal resorption fB-/- mice, aPL-IgG vs NH-IgG, 9.5 ± 2.4 vs 10.9 ± 2.1), indicating a role for the alternative pathway in fetal damage. This report, taken together with our previous work, shows that fB, C5 and C5aR are required for pregnancy complications triggered by aPL antibodies. Specifically, we identified the proinflammatory sequelae of C5a–C5aR interactions and the recruitment of neutrophils as the critical intermediates linking pathogenic aPL antibodies to fetal damage. Our findings identify the key innate immune effectors engaged by aPL antibodies that mediate poor pregnancy outcomes and provide novel and important targets for the prevention of pregnancy loss in antiphospholipid syndrome.

Low serum C3, properdin, and C5 levels found in the acute stage of acute post-streptococcal glomerulonephritis (APSGN) indicate the presence of aggressive complement activation. We followed serum complement component levels in a child hospitalized with erysipelas who developed APSGN on the 2nd hospital day. Her initial serum sample, obtained prior to the clinical onset of nephritis, had a low properdin level and normal C3 and C5 levels despite the presence of C3 splitting activity. Two days later she developed gross hematuria and subsequent sera contained low C3, properdin, and C5 levels, as is usual in APSGN. These observations suggest that complement activation, predominantly through the alternative pathway, precedes the clinical onset of APSGN.

Genetic linkage between the HL-A and Bf loci could be confirmed in 43 families with 168 offspring. In 4 families, 5 recombinants out of 82 informative meiotic divisions were observed (r = 6.1%). The localisation of the Bf marker system was studied in 3 families with crossovers between HL-A and MLC. From these data the following map order of human chromosome 6 can be proposed: HL-A (1st locus) -- HL-A (2nd locus)--MLC-Bf---PGM(3). The fact that important components of the classical and alternate pathway of complement activation are governed by genes closely linked with HL-A and MLC loci leads to the proposition to include the Bf system into the Major Histocompatibility Complex in man.

The Henoch-Schönlein-syndrome, or anaphylactoid purpura, is usually a childhood disease. The progess of this syndrome in adults was observed in 4 cases at our clinic. An elevated IgA level in the serum with a normal complement value seems to be of immunological interest. By immunohistological methods fibrin and IgA could be demonstrated in skin and kidney biopsies; in glomerulae C3c was observed, occasionally accompanied by Properdin-factor-B. These findings differentiate this disease from other allergic superficial vasculitids by the detection of IgG and complement; while at the same time some similarities are indicated to the so called "Berger Nephritis" with comparable kidney findings.

An epidemiological investigation was made of eight employees working in a defined section of an office building who complained of febrile reactions accompanied by respiratory tract symptoms and fatigue. Culture of the water from the humidifier for their section yielded strains of Pseudomonas acidovorans and an unidentified Pseudomonas species. In vitro studies showed that these strains activated the alternative pathway of the complement system in Mg-EGTA supplemented serum, as evidenced by properdin depletion and conversion of C3-proactivator (Factor B) and C3. Whereas the employees with symptoms had significantly reduced properdin values during the symptomatic phase, a slight C3 conversion and antibodies to Pseudomonas spp., staff working in another part of the building with a different ventilation system did not. It was concluded that staff with humidifier fever symptoms had been exposed to Pseudomonas spp. through the faulty ventilation system, and their symptoms were most likely a result of complement activation.

Properdin is a plasma glycoprotein which stabilizes the C3bnBb¯ enzyme complex of the alternative pathway of the complement system1,2. Unlike the classical pathway, which is initiated by interaction of C1q with the Fc regions of IgG or IgM antibodies in immune complexes, the alternative pathway can be directly activated via binding of C3b to surfaces of foreign organisms3,4. The stabilized C3bnBbP¯ complex activates components C3 and C5 resulting in opsonization of foreign material (via C3b) and assembly of the membrane attack complex (via C5b) on target cells. Therefore properdin greatly enhances complement-mediated clearance and inactivation mechanisms in both natural and acquired resistance to infection1,4. This paper shows that the primary amino acid sequence of properdin is composed mainly of six repeating motifs, each of ∼60 amino acids, and that similar sequences are found in thrombospondin5, the circumsporozoite protein of malaria parasites6–8 and regions of the membrane-attack components of complement9. These similarities may provide insight into the mechanisms by which parasites avoid host defences mediated by complement.

Properdin factor B phenotypes were determined in 7 Bantu speaking Negroid populations, 1 Indian, and 1 Colored population of South Africa in a total of 1258 individuals. In the Negroid populations allele frequencies were: BfF 0.655, BfS 0.282, BfRARE 0.063, in the Indian population: BfF 0.322, BfS 0.645, BfRARE 0.033, and in the Colored population: BfF 0.513, BfS 0.435, BfRARE 0.052. In addition, 2 so far unknown F alleles and possibly 1 new S allele were discovered.

Summary: We report correlative studies of factor B, properdin, C3, and the serum opsonic activity for Escherichia coli and Staphylococcus aureus in patients with the idiopathic nephrotic syndrome (INS). Thirty-two patients with the idiopathic nephrotic syndrome were studied. Twenty-two patients were steroid responsive (Group I), of which 11 patients were steroid dependent. Ten patients were steroid resistant (Group II). The presence of the nephrotic syndrome (regardless of steroid responsiveness) was associated with a significantly reduced mean serum factor B concentration. Of the complement components studied, only factor B was significantly decreased during relapse (factor B 24.8 ± 9 μg N/ml in INS versus 46 ± 12 μg/ml in normal, P < 0.001). When the combined groups were studied during remission of INS, the mean serum factor B concentrations were not different from normal. Similar results were found when each group was examined separately. Ten patients had serum factor B determinations during both exacerbation and remission of the nephrotic syndrome. The serum factor B increased in nine patients and was unchanged in one. A highly positive correlation between serum factor B and scrum albumin concentrations was present (r = +0.805, P < 0.001). Twenty sera from 14 patients with the nephrotic syndrome, studied at various stages of the nephrotic syndrome, were evaluated for opsonization titers of E. coli employing the bacterial killing assay. Eleven sera from seven patients had reduced capacity for E. coli opsonization, i.e., bacteria were not opsonized in 2% serum. There was a significant difference between the mean factor B concentrations of sera with abnormal as compared to normal opsonization of E. coli (P < 0.001). The serum of one patient with nephrosis opsonized E. coli normally 60 min after the addition of isolated factor B. The opsonic activity of serums from three additional patients with relapse of INS were studied by determining uptake of radiolabeled E. coli by normal leukocytes. The addition of isolated factor B increased phagocytosis in the serum from two of three patients. Decreased opsonization of S. aureus was found in only 3 (two patients) of 19 sera. The complement components, C1q, C4, properdin, and C3, were normal during both periods of exacerbation and remission with the exception that C4 was significantly elevated during remission of nephrosis. These results suggest that a significant decrease of serum factor B concentration is associated with abnormal opsonization of E. coli. We do not know the cause of decreased serum factor B, but renal pathologic findings do not appear to be of etiologic importance. The high correlation of serum factor B with scrum albumin concentration suggests that factor B, with a molecular weight of 80,000, was being lost in the urine. Speculation: The increased incidence of severe infections such as peritonitis, which occurs in INS patients, may be the result of reduced serum factor B, a component of the alternative pathway. Although further work is necessary to determine the cause of factor B decrease in INS and the role of other scrum factors in this opsonic defect, the understanding of the role of factor B in the predilection of nephrotic patients to certain infections could be of great importance in the care of these patients.

The phagocytic activity of the leukocytes and the serum complement, properdin, and lysozyme levels were studied in germfree miniature piglets and similar animals ocntaiminated withEscherichia coli 055 andE. coli 083. In the presence of autologous serum and complement phagocytosis ofE. coli 055 cells was inhibited, but it was considerably intensified under the influence of specific opsonins (antibodies againstE. coli 055). Lowered levels of complement, properdin, and lysozyme were found in the germfree animals. After peroral monocontamination withE. coli the formation of properdin and complement was stimulated the most, and that of lysozyme the least. Antibodies againstE. coli 055 were not found in the monocontaminated piglets. The highest lysozyme levels were found in the previously germfree animals, which points to the role of other contamination factors thanE. coli cells in the stimulation of lysozyme. It is concluded that microbial contamination plays an important role in the development of the cellular and humoral factors of resistance.

Since the estimation of recombination fractions is only an arbitrary means to map genetic loci on chromosomal regions, family studies of cases with informative cross-overs within the region in question are of decisive importance. This paper reports the study of a family with a HLA-B to HLA-D cross-over which is informative in the Bf system. The possible reasons for conflicting published data on Bf gene mapping are discussed.

Complete absence of Factor I (C3b inactivator) was found in the serum of a 3-year-old boy with recurrent polytope bacterial infections. Analysis of the complement (C) components of the patient's serum showed that while serum levels of the earlier C components (C1q, C1r, C1s, C4, and C2) were within the normal range, levels of C3, C5, Factor B, and properdin were decreased significantly. Factor H (β1H) was also decreased and, by crossed immunoelectrophoresis, migrated to the alpha region (Hα). C-dependent biological functions such as chemotactic activity, opsonic factors, immune adherence inhibition, and intracellular killing of bacteria were defective. The patient has been treated with fresh frozen plasma (10 ml/kg body weight) every 4 weeks for 2 years. Most of the C-derived biological functions improved, and Factor H regained beta electrophoretic mobility (Hβ) following plasma infusion. During the period of treatment, the child has been free of bacterial infections. Mild anaphylactic reactions to the plasma occurrred on two occasions; the other 22 infusions were well tolerated.

Spontaneous bacterial peritonitis (SBP) is a common complication of advanced liver disease, which has a reported prevalence of between 4 and 27%. Frequent bacteremias due to inadequate host defense mechanisms, particularly the reticuloendothelial system (RES), with seeding of an ascitic fluid that lacks a normal opsonic activity, is believed to be the principal cause of SBP. Little data exist as to the role of serum levels of complement and immunoglobulins as well as the cell-mediated immune system in the pathogenesis of SBP. The aim of this study was to determine the serum levels of the third and fourth components of complement (C3, C4), total hemolytic complement activity (CH100), and properdin factor B (PFB) and immunoglobulins G, A, and M and various T-cell parameters in individuals admitted to hospital with ascites and advanced liver disease and to determine whether one or more of these factors could be used to predict the development of SBP in patients with advanced liver disease. Fourteen consecutive patients (nine male and five female; age 47.5±3.1 years, mean±Sem) with end-stage liver disease and ascites, who were evaluated for possible liver transplant at the University of Pittsburgh and who developed SBP, comprised the study group. The diagnosis of SBP was determined by positive ascitic fluid culture (three patients) and/or ascitic fluid neutrophil count of>250 cells/mm3 (all patients). The control group consisted of 14 patients, matched for type of liver disease, age, and sex, who did not develop SBP. Each patient studied underwent a prospective elective abdominal paracentesis, and the recovered fluid was assayed for total protein, total white blood cell count, total neutrophil count, and culture. The immunological status of each individual was accomplished by determining the serum levels of C3, C4, PFB, CH100, and immunoglobulins G, A, and M. Finally the percentage of lymphocytes and their distribution in the various T-cell subsets was determined also. No difference in the immunological status between these two groups was evident. However, the ascitic fluid protein level, although not significantly different between the two groups studied, was less than 2 g/dl more often in the group developing SBP than in the control group that did not subsequently develop SBP. The estimated risk for developing SBP in individuals with ascitic fluid protein level of

A protein-bound polysaccharide from mycelia of Coriolus versicolor PS-K, clinically used as an immunomodulator, has been shown to restore the decreased cellular immune response and to exhibit host-mediated antitumor activity. In this experiment, PS-K was found to increase serum complement level in guinea pig and in human without malignancy, when hemolytic assay of complement was performed using sensitized sheep erythrocytes for the classical pathway activity and unsensitized rabbit erythrocytes for the alternative pathway activity. Assay of complement components revealed increase in C3 level in guinea pig, but no significant changes in C1q, C4, C3, properdin, C3 activator, and C1-inhibitor in human, while C5 and C9 were depressed. Conversion of beta 1C to beta 1A was observed in the 7th day's plasma of these patients by crossed immunoelectrophoresis. Biosynthesis of guinea pig C3 was accelerated by administration of PS-K, but that of C4 was not affected. These evidences suggested that PS-K might potentiate immune response of the host by elevating serum complement level, in addition to the activation of the complement system.

Circulating immune complexes by fluid phase Clq binding assay, complement components and anti-immunoglobulin levels were studied in sera of 35 patients with rheumatoid arthritis (RA). In 23 of the 35 sera (65.7%), circulating immune complexes were positive, and the mean +/- SD of Clq binding activity (ClqBA), 44.5 +/- 19.4%, was significantly high compared to that of healthy persons, 17.4 +/- 8.2%. Antigenic determination of complement components revealed that Clq, C3, C5, C9, factor B and Cl esterase inhibitor (ClINH) were significantly high in sera of RA, but C4 and properdin were not. The disease activity correlated with ClqBA, IgG- and IgM-anti-immunoglobulins, C9 and serum IgG. On the other hand, ClqBA correlated with both IgG- and IgM-anti-immunoglobulin levels but not with complement components.

Activation of C3 and factor B in normal human serum by P. ovale was demonstrated using a standard unidirectional immunoelectrophoresis technique. Activation of complement by the alternative (properdin) pathway is a possible mechanism by which P. ovale may mediate an inflammatory response.

Three of four children in a family have homozygous (less than 1% of normal) deficiency of factor H of the complement system and both parents, who are first cousins, are heterozygous for the same defect. The father and two of the H-deficient siblings also have a partial C2 deficiency. One of the children with combined deficiencies is affected by systemic lupus erythematosus with nephritis. No increased susceptibility to infections has been observed in the family. H deficiency is inherited in an autosomal codominant manner and is independently transmitted from C2 deficiency and HLA haplotypes. In the homozygous state it is associated with very low serum concentrations of B and C3, barely demonstrable as activated molecules. C5 is greatly reduced (less than 5%). Also, properdin and C6-9 are decreased. The findings in this family demonstrate that the occurrence of systemic lupus erythematosus in one of the children affected by a combined deficiency of factor H and C2 raises the question whether this pathology is related to the complete factor H or to the heterozygous C2 deficiency. Complete H deficiency is not necessarily accompanied by overt illness.

A variant band in the Bf polymorphism has been found in the serum of a healthy women, her mother, her sister, and two brothers. By direct comparison the band was found to migrate faster than F but slower than F1. It is highly probable that the band represents a new allele at the Bf locus, Bf 0.55. The new allele was transmitted in this family together with the HLA haplotype A11, B27.

C3 and C4 serum complement component levels were examined during various stages of disease activity in 14 SLE patients. It was found that C3 levels were more sensitive index of disease activity than those of C4. C3 levels lower than C4 as expressed by a C3/C4

Immunofluorescence studies were performed in 12 cases of herpes gestations. Direct IF staining (performed in 10 of them) revealed a highly characteristic pattern, notably 1) Constantly BMZ deposits of complement component C3, 2) In most biopsy specimens also C4 and C5, 3) Deposits of C4, C5, properdin and IgG variable in different specimens of given patients. About half of the specimens examined contained properdin and about one third stained for IgG, 4) Findings of IgM, IgA, IgD and IgE were consistently negative, 5) Serum findings of BMZ antibodies in given cases were variable. In two cases circulating BMZ antibodies were detected in one of the samples examined. On the base of these findings it seems that HG is related to BP.

An Hand von 19 Fallen wird das Verhalten von Properdin, Komplement (C′) und der C′3-Komponente des Komplements nach typischen gynakologischen Operationen mit unterschiedlichem Gewebstrauma studiert. Dabei last sich folgendes feststellen: 1. Bei der posttraumatischen Entzundung sinkt der Properdinspiegel relativ rasch ab, verharrt einige Tage auf niederen Werten und steigt bis zum 10., spatestens 15. Tag wieder auf die Ausgangswerte. Das Komplement (C′) zeigt keine deutlichen Veranderungen. Die 3. Komplementkomponente (C′3) fallt am 1. Tag ab und steigt bis zum 3. Tag uber den Ausgangswert wieder an. 2. Beim Vergleich zwischen den Verlaufen nach Totalexstirpationen des Uterus als schwere Traumen und den Scheidenplastiken als leichte Traumen finden sich keine eindeutigen Unterschiede (im Gegensatz zu fruher beobachteten Serumeiweisveranderungen). 3. Die Aufschlusselung der untersuchten Falle im Hinblick auf die angewandte Thrombose-Prophylaxe mit einem Cumarinderivat ergibt keine deutlichen Unterschiede gegenuber den nichtbehandelten Patientinnen. 4. Das Verhalten von Properdin und α2-Globulinen bei posttraumatischer Entzundung ist zwar gegensinnig, aber zeitlich eindeutig gegeneinander verschoben, so das eine gegenseitige Beeinflussung in vivo schwer vorstellbar ist. 5. Auf die moglichen Zusammenhange zwischen Properdinbindung durch Polysaccharide, Cytolyse, Gewebszerfallsgrose und α2-Globulinvermehrung wird hingewiesen.

This work deals with an experimental analysis of the two possible methods of properdin determination and their disadvantages. The authors suggest a new simple method which consists of the substitution of Rp by a guinea pig complement with the utilization of normal rat serum (characterized by high and stable properdin titer) as a standard. The optimal dilution of the complement, which loses its hemolytic activity after treatment with rat serum in 1:600–1:800 dilution in presence of zymosan, is determined in a preliminary experiment. The amount of the serum under investigation capable of giving the same result with the titrated dose of complement, is determined in the main experiment.

As shown in experiments on dogs single acute blood loss causes a rapidly appearing and considerable reduction of blood properdin. Gradual normalization of properdin level was observed in 2–5 days after blood loss. With repeated blood loss the tolerance of the properdin system developed quickly, and no properdin level drop was provoked by blood exfusions. It is suggested that the changes of the properdin system activity are one of the factors causing a lower resistance to infection in animals which sustained an acute blood loss.

Es wird erstmalig uber die Konzentration der einzelnen Komplementfaktoren bzw. des Properdins im Nabelvenenserum bzw. im Serum des gesunden Sauglings berichtet.

1. Nach einem kurzen Uberblick uber den gegenwartigen Stand des Properdinproblems wird hervorgehoben, das das Properdin-Komplement-System beim physiologischen Zellabbau und bei der Blutmauserung moglicherweise beteiligt ist. 2. Eine Anordnung zum Studium der Lyse von Erythrocyten in homologem Serum wird beschrieben. Es wird gezeigt, das fur die Lyse die Gegenwart der 4 bekannten Komplementfaktoren, von Properdin und von Ca++, bzw. Mg++-Ionen erforderlich ist. 3. Die Steigerung der unspezifischen Lyse gelingt durch Vorbehandlung mit proteolytischen Fermenten (Plasmin, Thrombin). Diese Vorschadigung scheint nach bisherigen Ergebnissen von Bedeutung zu sein bei klinischen Zustanden, die mit einer Aktivierung der Fibrinolyse im Plasma einhergehen. 4. Die Steigerung der unspezifischen Lyse gelingt weiter nach Schadigung der Erythrocyten mit den cytotoxischen Kernproteinen Protamin und Histon; weiter durch hinzugefugte Zellkerne und Leukocyten. 5. Zusatz von Histon, Zellkernen und myeloischen Leukocyten ruft Verdoglobinbildung und schlieslich Entfarbung von Hamoglobin hervor. Auf die mogliche Bedeutung dieses Befundes fur die „anikterischen hamolytischen Anamien“ bei Erkrankungen mit gesteigertem Zellzerfall wird hingewiesen. 6. Es wird gezeigt, das die unspezifische Lyse — auch die vorgeschadigter Erythrocyten — in vitro gehemmt werden kann durch Purinnucleoside. Die mogliche Bedeutung fur die Therapie toxisch-hamolytischer Erkrankungen wird diskutiert.