Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Properdin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed2003

Host genetic determinants of Neisseria meningitidis infections.

The clinical presentation of infections caused by Neisseria meningitidis is highly diverse. Some patients develop meningitis, and others present with sepsis or even septic shock. After invasion of the bloodstream by the bacteria, three main cascade pathways are activated. These are the complement system, the inflammatory response, and the coagulation and fibrinolysis pathway. These pathways do not act independently but are able to interact with each other. Genetic polymorphisms among components of these pathways have been shown to be involved in the susceptibility, severity, and outcome of meningococcal disease. We review knowledge of genetic variations associated with susceptibility to and severity of meningococcal infection. Complement deficiencies and defects in sensing or opsonophagocytic pathways, such as the rare Toll-like receptor 4 single nucleotide polymorphisms (SNPs) and combinations of inefficient variants of Fcgamma-receptors, seem to have the most important role in genetically established susceptibility. Effect on severity has repeatedly been reported for FcgammaRIIa and plasminogen activator inhibitor type 1 (PAI1) polymorphisms. Outcome effects have been confirmed for SNPs in properdin deficiencies, PAI1 and combination of the -511C/T SNP in interleukin 1beta, and the +2018C/T SNP in interleukin RN. Conflicting results are reported for the effect of the -308G/A promoter polymorphism in tumour necrosis factor (TNF) alpha. These differences may reflect discrepancies in group definitions between studies or the influence of additional SNPs in the TNFalpha promoter, which can form haplotypes representing different cytokine production capacity. For several SNPs, the potential effect on susceptibility, severity, or outcome has not yet been confirmed in an independent study.

Child↗
PubMed2004

Pulmonary complications of primary immunodeficiencies.

In the fifty years since Ogden Bruton discovered agammaglobulinemia, more than 100 additional immunodeficiency syndromes have been described. These disorders may involve one or more components of the immune system, including T, B, and NK lymphocytes; phagocytic cells; and complement proteins. Most are recessive traits, some of which are caused by mutations in genes on the X chromosome, others in genes on autosomal chromosomes. Until the past decade, there was little insight into the fundamental problems underlying a majority of these conditions. Many of the primary immunodeficiency diseases have now been mapped to specific chromosomal locations, and the fundamental biologic errors have been identified in more than 3 dozen. Within the past decade the molecular bases of 7 X-linked immunodeficiency disorders have been reported: X-linked immunodeficiency with Hyper IgM, X-linked lymphoproliferative disease, X-linked agammaglobulinemia, X-linked severe combined immunodeficiency, the Wiskott-Aldrich syndrome, nuclear factor kappaB essential modulator (NEMO or IKKg), and the immune dysregulation polyendocrinopathy (IPEX) syndrome. The abnormal genes in X-linked chronic granulomatous disease (CGD) and properdin deficiency had been identified several years earlier. In addition, there are now many autosomal recessive immunodeficiencies for which the molecular bases have been discovered. These new advances will be reviewed, with particular emphasis on the pulmonary complications of some of these diseases. In some cases there are unique features of lung abnormalities in specific defects. Infections obviously account for most of these complications, but the host reaction to infection often leads to characteristic findings that can be helpful diagnostically. Finally, advances in treatment of the underlying diseases as well as their infectious complications will be covered.

Agammaglobulinemia↗
PubMed2002

Biophysical characterization, including disulfide bond assignments, of the anti-angiogenic type 1 domains of human thrombospondin-1.

Thrombospondin-1 (TSP1), a modular secreted glycoprotein, possesses anti-angiogenic activity both in vitro and in vivo. This activity has been localized to the thrombospondin type 1 repeats/domains (TSR). A TSP1 monomer contains three TSRs, each with a hydrophobic cluster with three conserved tryptophans (WxxWxxW), a basic cluster with two conserved arginines (RxR), and six conserved cysteines. Using the baculovirus system, we expressed TSRs of human TSP1 as either the three domains in tandem (P123) or the third domain alone (P3) and demonstrated that both P123 and P3 at nanomolar concentrations inhibit either basic fibroblast-growth-factor or sphingosine-1-phosphate induced endothelial cell migration. Far-UV circular dichroism (CD) indicated that P123 and P3 have a common global fold that is very similar to properdin, a protein with six TSRs. Near-UV CD and fluorescence quenching studies indicated the conserved tryptophans are in a structured, partially solvent-accessible, positively charged environment. N-terminal sequence and mass spectrometry analysis of trypsin-digested TSRs indicated that the RFK linker sequence between P1 and P2 is readily proteolyzed and the conserved arginines are solvent accessible. By a combination of proteolysis and mass spectrometry, the recombinant TSRs were determined to be fully disulfide bonded with a connectivity of 1-5, 2-6, and 3-4 (cysteines are numbered sequentially from N- to C-terminus). TSRs are found in numerous extracellular proteins. These TSRs share the hydrophobic and basic clusters of the TSP TSRs but some have quite different placement of cysteine residues. We propose a sorting of TSRs into six groups that reconciles our results with information about other TSRs.

Amino Acid Sequence↗
PubMed2000

New genetic variation in European hares, Lepus granatensis and L. europaeus.

Six genetic polymorphisms for the Iberian hare (Lepus granatensis) and four for the brown hare (L. europaeus) are newly described. The genetic variation of peptidases B (PEPB) and C (PEPC), hemoglobin alpha chain (HBA), hemopexin (HPX), vitamin D binding protein (GC), and properdin factor B (BF) was assessed by conventional electrophoresis and isoelectric focusing in carrier ampholytes and hybrid pH gradients. Six alleles were detected in PEPB, three in PEPC, four in HBA, six in GC, five in HPX, and six in BF. At least one allele was shared between species at all loci except HBA. The allelic overlap between the two species was medium to high in PEPB, GC, and HPX and small in PEPC and BF.

Alleles↗
PubMed1999

Immunohistologic evaluation of mechanisms mediating hyperacute lung rejection, and the effect of treatment with K76-COOH, FUT-175, and anti-Gal column immunoadsorption.

Although most investigators agree that lung dysfunction occurs rapidly in various pig-to-primate hyperacute lung rejection (HALR) models, the basic mechanisms mediating this phenomenon remain in question. Here we describe an immunohistochemical method for assessment of mechanisms driving HALR. Using an established model wherein piglet lungs are perfused ex vivo with human blood, six experimental groups (K76 COOH; FUT-175; K76 with FUT; anti-alpha-Gal column adsorption; column with FUT; and column with K76) and two control groups (unmodified human blood; autologous pig blood) were studied. Each lung was biopsied serially during perfusion, and assessed using an immunohistochemical technique, with vWF staining as an internal control to quantitate binding of human IgM, IgG, C3, C5b-9, properdin, and C1q. The effect of each treatment and subsequent lung perfusion on IgG and IgM anti-alpha-Gal titers(by ELISA) and on pig endothelial cell cytotoxicity were correlated with histologic findings. We found that [1] the classical complement activation pathway was activated, as has been shown for other pig organs in primate or human blood environments [2]; alternative complement pathway activation is also seen, which has not been described for other organs in pig-to-primate models, but only in the context of classical pathway activation; and [3] anti-Gal column absorption, pharmacologic inhibition of complement, or combination therapy each was associated with histologic evidence of partial protection, consistent with what would be predicted for each intervention. Further, immunohistologic differences correlated with physiologic outcomes [8] and with antibody assay results, and revealed that treatments used were incompletely effective. Our data suggest that more complete inhibition of antibody- and complement-driven pathways than was achieved in these experiments will be necessary to prevent the antibody and complement-mediated facets of hyperacute lung rejection. This immunohistologic technique may also help us identify additional pathogenic mechanisms important to eventual clinical application of pig-to-human lung xenografts.

Acute Disease↗
PubMed2001

Complement deposition in renal allografts with early malfunction.

Among patients with early severe impairment of renal allograft function we have previously identified a group displaying isolated deposition of complement factor C3 in glomeruli. Here we studied the pattern of complement deposition more extensively in allograft biopsies from five patients using an immunofluorescence technique. We found a prominent deposition of C3c, C3d and C4d antigens in the glomerular capillary walls, and a positive reaction to vitronectin (S-protein), but only trace amounts of the complement factor C9 neoepitope. Clq, C4c, C3a, iC3b, factor B, properdin, immunoglobulins IgG, IgA or IgM were not found in glomeruli or in any other cortical structure. These findings indicate that most of the demonstrated glomerular C3 consists of C3b and/or C3c/C3d molecules. By immunoelectron microscopy the C3 antigen was found within the glomerular basement membrane. Our findings indicate that there is a mechanism of complement activation involving the early steps of the classical pathway, despite the lack of demonstrable immunoglobulins in the tissue. In analogy with similar reactions described recently in heart allografts, we suggest that this may be a manifestation of a humoral rejection, possibly mediated by a low titer of circulating antibodies directed against endothelial surface antigens, presumed to be the initial step leading to complement activation.

Adult↗
PubMed1976

Complement activation in vivo in cancer patients receiving C. parvum immunotherapy.

Serum complement levels were assayed in 26 patients with disseminated cancer, who received immunotherapy with infusion of C. parvum. Complement activation, indicated by the consumption of C3 or C4 or both, was found in 46% of the patients. Serum samples showed direct correlation between decreased C3 and conversion of C3 proactivator, whereas such conversion did not occur when C4 alone was decreased. It is concluded that the bypass (properdin) pathway was activated in patients in whom C3 consumption was detected, while the classical (C1) pathway was activated in the patients with C4 consumption unaccompanied by C3 decrease. Direct correlation was observed between delayed cutaneous hypersensitivity reactions to recall antigens and the incidence of C. parvum-associated complement activation.

Complement C3↗
PubMed1977

Detection of circulating immune complexes in patients with glomerulonephritis.

A panel of three immune complex (IC) assays was used in this study to test sera from patients with glomerulonephritis (GN): the Raji cell radioimmune assay (IRCA), the radio-labeled C1q binding assay (IC1qBA), and the microcomplement consumption test (MCT). The sensitivity and specificity of each assay was evaluated in preliminary studies, and the greater sensitivity (5 to 10microgram of aggreagated human gamma-globulin (AHG) per ml of serum) and IgG specificity of the IRCA was apparent. Problems related to the preliminary heat inactivation of test sera, the interaction of C1q with substances other than IC, and the effects of suboptimal storage of test sera were experienced with the MCT and, to a lesser extent the IC1qBA. The individual reactivities of the different assays were exploited by using them in combination. Thus ICs were detected by one or more of the assays in 87% of patients with systemic lupus erythematosus (SLE), 65% of patients with GN associated with other systemic diseases, and 39% of patients with primary GN. ICs were detected more frequently in patients with acute GN than chronic GN, and in patients with low serum C3, C4, and properdin factor B (C3PA) levels.

Acute Disease↗
PubMed1987

Complement activation in IgA nephropathy.

Activation of alternative complement pathway is presumed to be important pathogenically in IgA nephropathy since renal biopsies usually exhibit glomerular deposition of C3 and P (properdin). Surprisingly, little is known about plasma complement activation in this disease, and the plasma C3 and C4 concentrations are usually normal or increased. We quantitated C3 activation in 202 plasmas from 81 patients with IgA nephropathy using a sensitive new assay that detects a neoantigen [iC3b-C3d neoantigen) which appears when C3b is inactivated to iC3b, C3dg, or C3d. This assay accurately quantitates small amounts of in vivo C3 activation. The concentration of iC3b-C3d neoantigen in plasma was significantly increased, indicating C3 activation in 37% of the pediatric and 57% of the adult plasmas assayed. When data from serial determinations in the patients were analyzed, 75% of the adult and 57% of the pediatric patients had C3 activation on at least one occasion. Classical pathway activation, quantitated by C4 activation was found in 20% of the adult and 5% of the pediatric plasmas. No association was found between elevated iC3b-C3d neoantigen concentration and history of macroscopic hematuria, chronic renal insufficiency or degree of proteinuria. These studies show that complement activation can frequently be detected in the plasma of IgA nephropathy patients. However, the pathophysiologic significance of this complement activation remains to be determined.

Adult↗
PubMed1987

Complement membrane attack (MAC) in idiopathic IgA-glomerulonephritis.

Antigens of the membrane attack complex of complement (MAC), such as C5, C6, C9 and MAC-related neoantigen(s), were demonstrated in the mesangium of 23 cases with IgA-glomerulonephritis (IgA-GN) and two cases with Henoch-Schönlein purpura nephritis (HSP). High specificity of the polyclonal antibodies was verified by dot-blot analysis. Control specimens lacking immunoglobulin deposits were negative for MAC-related antigens. Markers of classical pathway activation (Clq and C4) were observed only in two of 24 and one of 23 cases of IgA-GN and HSP, respectively. Glomerular distribution patterns (mesangial vs. mesangio-peripheral) of immunoglobulin or complement deposits were correlated for IgA and C3b/iC3b (P less than 0.002), for IgA and properdin (P less than 0.002) and for IgA and MAC neoantigens (P less than 0.01). Double immunostaining experiments revealed co-localization of IgA and MAC neoantigens at identical mesangial and capillary sites. Glomerular distribution of the less pronounced IgG or IgM deposits did not correlate with that of any complement-derived antigen. The pattern of MAC-related antigens was found to be uniformly either mesangial or mesangio-peripheral. Staining for MAC-related antigens was less intense in IgA-GN cases with minimal glomerular lesions than in cases with more advanced non-sclerosing lesions. IgA, C3d, and MAC localized in corresponding glomerular sites. This is consistent with complete local activation of complement by glomerular IgA deposits via the alternative pathway. The possibility exists that MAC plays a pathogenetic role, such as by irritation of bystander cells, in IGA-GN and HSP.

Adolescent↗
PubMed1994

Alternative pathway activation of complement by cultured human proximal tubular epithelial cells.

Human proximal tubular epithelial cells (PTEC) incubated with normal human serum (NHS) were found to fix on their surface C3, properdin, terminal complement components and C5b-9 MAC neoantigen, but not C1q and C4, by immunofluorescence. Complement fixation was abrogated if PTEC were incubated with EDTA-treated NHS or C3-deficient human serum, but not with Mg EGTA-treated NHS or C1q-deficient human serum, showing the prevalent activation of the alternative pathway of complement. This event was followed by marked cytoskeleton alterations with disruption of the actin cortical network, redistribution of actin throughout the cytoplasm and formation of blebs, and by cell cytolysis. In addition, superoxide anion and hydrogen peroxide production and chemiluminescence response were detected in consequence of MAC insertion on PTEC plasma membrane. The dependency on MAC of the observed biological effects of complement fixation on PTEC surface was shown by using sera selectively deficient of terminal components of complement (C6 or C8), and therefore unable to form the C5b-9 MAC, and by restoring the ability to form MAC after addition of purified C6 or C8. The possible pathogenetic relevance of these observations in tubulointerstitial injury occurring in patients with complementuria due to non-selective proteinuria, is discussed.

Blood↗
PubMed2006

The structure of complement C3b provides insights into complement activation and regulation.

The human complement system is an important component of innate immunity. Complement-derived products mediate functions contributing to pathogen killing and elimination. However, inappropriate activation of the system contributes to the pathogenesis of immunological and inflammatory diseases. Complement component 3 (C3) occupies a central position because of the manifold biological activities of its activation fragments, including the major fragment, C3b, which anchors the assembly of convertases effecting C3 and C5 activation. C3 is converted to C3b by proteolysis of its anaphylatoxin domain, by either of two C3 convertases. This activates a stable thioester bond, leading to the covalent attachment of C3b to cell-surface or protein-surface hydroxyl groups through transesterification. The cleavage and activation of C3 exposes binding sites for factors B, H and I, properdin, decay accelerating factor (DAF, CD55), membrane cofactor protein (MCP, CD46), complement receptor 1 (CR1, CD35) and viral molecules such as vaccinia virus complement-control protein. C3b associates with these molecules in different configurations and forms complexes mediating the activation, amplification and regulation of the complement response. Structures of C3 and C3c, a fragment derived from the proteolysis of C3b, have revealed a domain configuration, including six macroglobulin domains (MG1-MG6; nomenclature follows ref. 5) arranged in a ring, termed the beta-ring. However, because neither C3 nor C3c is active in complement activation and regulation, questions about function can be answered only through direct observations on C3b. Here we present a structure of C3b that reveals a marked loss of secondary structure in the CUB (for 'complement C1r/C1s, Uegf, Bmp1') domain, which together with the resulting translocation of the thioester domain provides a molecular basis for conformational changes accompanying the conversion of C3 to C3b. The total conformational changes make many proposed ligand-binding sites more accessible and create a cavity that shields target peptide bonds from access by factor I. A covalently bound N-acetyl-l-threonine residue demonstrates the geometry of C3b attachment to surface hydroxyl groups.

Animals↗
PubMed1981

The conversion of human complement component C5 into fragment C5b by the alternative-pathway C5 convertase.

The cleavage of human complement component C5 to fragment C5b by the alternative pathway C5 convertase was studied. The alternative-pathway C5 convertase on zymosan can be represented by the empirical formula zymosan--C3b2BbP. Both properdin-stabilized C3 and C5 convertase activities decay with a half life of 34 min correlating with the loss of the Bb subunit. The C5 convertase functions in a stepwise fashion: first, C5 binds to C3b and this is followed by cleavage of C5 to C5b. The capacity to bind C3b is a stable feature of component C5, as C5b also has this binding capacity. Component C5, unlike component C3, does not form covalent bonds with zymosan after activation, and C5 is not inhibited by amines. Therefore C5, although similar in structure to C3, does not appear to contain the internal thioester group reported for C3 and C4.

Amines↗
PubMed1992

Human platelet glycoprotein IIIb binds to thrombospondin fragments bearing the C-terminal region, and/or the type I repeats (CSVTCG motif), but not to the N-terminal heparin-binding region.

Major blood membrane platelet glycoprotein IIIb (GPIIIb), also termed GPIV or CD365, has been identified as a receptor for thrombospondin (TSP), collagen and Plasmodium falciparum-infected erythrocytes. The aim of the present study was to identify region(s) of TSP involved in binding of GPIIIb. Proteolytic fragments of TSP (M(r) 140 kDa, 120-18 kDa and 27 kDa on SDS/PAGE under reducing conditions) were purified by f.p.l.c. and identified by N-terminal gas-phase sequencing, e.l.i.s.a. and Western blots using monoclonal antibodies directed against defined domains of TSP. The 140 kDa and 120-18 kDa fragments (C-terminal region), but not the 27 kDa fragment (N-terminal region), were shown to bind to GPIIIb by using e.l.i.s.a. and affinity-chromatography systems. TSP binding to a GPIIIb-affinity column was Ca(2+)-dependent and reduced by 45% in the presence of EDTA. Moreover, TSP was only partially eluted with EDTA from a Ca(2+)-equilibrated GPIIIb column. A fragment of 68 kDa, obtained by further digestion of the 140 kDa fragment, bound to the GPIIIb-Sepharose affinity column. This fragment, or stalk-like region, bears the TSP type I repeats that show sequence similarity to regions on properdin, Plasmodium falciparum proteins and antistasin. Peptides (CSVTCG or SVTCGGGV) representing these repeats bound isolated GPIIIb in a Ca(2+)-independent way, but did not completely inhibit the GPIIIb and TSP interaction. These studies indicate that GPIIIb binds to the TSP via the C-terminal region and/or the CSVTCG motif, but not to the N-terminal region. Interaction between GPIIIb and the TSP C-terminal region or the CSVTCG motif is respectively Ca(2+)-dependent and -independent.

Amino Acid Sequence↗
PubMed1997

Detection and quantification of the control proteins of the alternative pathway of complement in 3T3-L1 adipocytes.

The complement peptide C3a desarg is identical to acylation-stimulating protein (ASP), a human plasma protein that potently stimulates adipocyte triacylglycerol synthesis and glucose transport. Both human and murine adipocytes express mRNA and/or protein for the complement components C3 and factors B and D (adipsin) required to generate ASP. However, the regulatory mechanisms controlling this process are unknown. We have established a semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique to demonstrate the presence in mouse 3T3-L1 adipocytes of mRNA for all components of the alternative pathway, including the control proteins factors I and H, CR1 and properdin. On differentiation, mRNA for C3 (fivefold) and factor D (> 50-fold) increased, whereas stimulation with tumour necrosis factor (TNF)-alpha and interleukin (IL) 1 beta led to eightfold increases in factor B mRNA. Metabolic labelling followed by immunoprecipitation showed that factor B protein is normally present in small quantities, and is greatly increased by cytokine stimulation. The larger quantities of C3 and H proteins present were little affected, whereas levels of C3a increased on cytokine stimulation. These results suggest that the rate-limiting step in the cytokine-induced production of ASP in adipocytes is factor B synthesis.

3T3 Cells↗
PubMed1999

cDNA sequence coding for the alpha'-chain of the third complement component in the African lungfish.

cDNA clones coding for almost the entire C3 alpha-chain of the African lungfish (Protopterus aethiopicus), a representative of the Sarcopterygii (lobe-finned fishes), were sequenced and characterized. From the sequence it is deduced that the lungfish C3 molecule is probably a disulphide-bonded alpha:beta dimer similar to that of the C3 components of other jawed vertebrates. The deduced sequence contains conserved sites presumably recognized by proteolytic enzymes (e.g. factor I) involved in the activation and inactivation of the component. It also contains the conserved thioester region and the putative site for binding properdin. However, the site for the interaction with complement receptor 2 and factor H are poorly conserved. Either complement receptor 2 and factor H are not present in the lungfish or they bind to different residues at the same or a different site than mammalian complement receptor 2 and factor H. The C3 alpha-chain sequences faithfully reflect the phylogenetic relationships among vertebrate classes and can therefore be used to help to resolve the long-standing controversy concerning the origin of the tetrapods.

Amino Acid Sequence↗
PubMed1999

Thrombospondin peptides are potent inhibitors of mesangial and glomerular endothelial cell proliferation in vitro and in vivo.

BACKGROUND: Thrombospondin 1 (TSP1), a multifunctional, matricellular glycoprotein, is expressed de novo in many inflammatory disease processes, including glomerular disease. Short peptide fragments derived from the type I properdin repeats of the TSP1 molecule mimic anti-angiogenic and/or transforming growth factor-beta (TGF-beta)-activating properties of the whole TSP1 glycoprotein. We investigated the effects of D-reverse peptides derived from the type I domain of TSP1 in experimental mesangial proliferative glomerulonephritis in the rat (anti-Thy1 model), as well as their effects on cultured mesangial and glomerular endothelial cells. METHODS: Effects of TSP peptides on proliferation of mesangial or glomerular endothelial cells in culture after growth arrest or growth factor stimulation (fibroblast growth factor-2, platelet-derived growth factor-BB, 10% fetal calf serum) were measured by [3H]thymidine incorporation assay. Adhesion of rat mesangial cells (MCs) to a TSP-peptide matrix was assayed using an attachment-hexosaminidase assay. TSP peptides were intraperitoneally injected daily in rats that had received an intravenous injection of polyclonal anti-Thy1 antibody to induce mesangial proliferative glomerulonephritis. On biopsies from days 2, 5, and 8 of anti-Thy1 disease, mesangial and glomerular endothelial proliferation, matrix expansion, mesangial activation, and microaneurysm formation were assessed. Functional parameters such as blood pressure and proteinuria were also measured. RESULTS: An 18-amino acid peptide (type I peptide) with anti-angiogenic and TGF-beta-activating sequences decreased mesangial and glomerular endothelial cell proliferation in vitro and in vivo and reduced microaneurysm formation and proteinuria in experimental glomerulonephritis. Analogues lacking the TGF-beta-activating sequence mimicked most effects of the type I peptide. The mechanism of action of these peptides may include antagonism of fibroblast growth factor-2 and alteration of MC adhesion. The TGF-beta-activating sequence alone did not have significant effects on mesangial or glomerular endothelial cells in vitro or in experimental kidney disease in vivo. CONCLUSION: Peptides from TSP1 may be promising therapeutics in treating glomerular disease with mesangial and endothelial cell injury.

Amino Acid Sequence↗
PubMed1999

Combined administration of IgA and IgG anti-Thy-1 antibodies enhances renal inflammation in rats.

BACKGROUND: IgA nephropathy (IgAN) is the most common type of immunologically mediated glomerulonephritis (GN) and is characterized by deposition in the glomerular mesangium of IgA together with C3, C5b-9, and properdin. In patients, the codeposition of IgA together with IgG and/or IgM can lead to a more progressive course of disease. In Wistar rats, mesangial proliferative GN can be induced by the injection of mouse IgG anti-Thy-1 antibodies (ER4G). In contrast, the administration of mouse IgA anti-Thy-1 antibodies (ER4A) to rats results in isolated hematuria without detectable albuminuria and without detectable complement deposition. METHODS: To investigate the effect of the combination of IgA and IgG on glomerular injury, Wistar rats were injected with a limiting dose of ER4G in the presence or absence of ER4A in a dose able to induce hematuria. RESULTS: Although the limiting dose of ER4G or the dose of ER4A used did not induce significant albuminuria, the combination of ER4G and ER4A resulted in a synergistic increase in albuminuria. Microhematuria occurred in rats receiving either ER4A or ER4G alone or in combination. Although both ER4A or a limiting dose of ER4G induced minor increases in extracellular matrix expansion, the combination resulted in a pronounced, additive increased matrix expansion. CONCLUSION: We conclude that in this model of IgA-mediated glomerulopathy, a selective complement-dependent synergistic renal injury is induced in Wistar rats by glomerular codeposition of mouse anti-Thy-1 monoclonal isotypes.

Animals↗