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PubMed1986

[Subacute septicemia caused by Meningococcus of serogroup Y and acquired deficiency of complement C3 fraction].

The high frequency of meningococcal infections in patients with congenital deficiency of a component of the complement terminal pathway emphasizes the critical role of this system in host resistance against Neisseriaceae. We report the observation of a subacute septicaemia due to N. meningitidis serogroup Y. This girl had an acquired deficit of the C3 fraction of complement due to a high titre of C3 nephritic factor (C3NeF). There was no evidence of partial lipodystrophy or biological symptoms of glomerular disease. The meningococcal infection revealed this biological abnormality.

Child↗
PubMed1970

Characteristics of a non-complement-dependent C3-reactive complex formed form factors in nephritic and normal serum.

When serum from a patient with membrano-proliferative glomerulonephritis and normal serum are mixed at 37 degrees C, C3 is rapidly broken down to two more rapidly migrating components. In the mixture, a heat-labile pseudoglobulin, designated as the C3 nephritic factor or C3NeF, reacts with a pseudogolbulin in the normal serum, designated as cofactor, to form a C3 inactivator. By analogy with the cobra venom factor, the C3 inactivator is most likely a complex of the nephritic factor and cofactor. The complex has been designated as the C3 lytic nephritic factor or C3LyNeF. The reaction which results in the Formation of C3LyNeF requires the presence of Mg(++), is highly temperature sensitive but occurs very rapidly at 37 degrees C. In 20 min at 37 degrees C, C3LyNeF can break down over 80% of the C3 in a mixture of normal and nephritic serum. The two-step reaction which leads to C3 breakdown has an optimum pH ranging from 6.0 to 9.0. Experiments employing serum depleted of C4 and C2, as well as certain characteristics of the C3NeF system provide evidence that C3 breakdown with nephritic serum is not dependent on complement-inactivating immune complexes or on the action of convertase (C4, 2). Data relating rate of C3 breakdown to the concentrations of C3NeF, C3, and C3LyNeF in the reaction mixture are similar to those for the reaction of enzyme with substrate. The biological significance of C3LyNeF in the production of glomerular inflammation has not been established.

Antigen-Antibody Reactions↗
PubMed1990

Quantitation of C4 nephritic factor by an enzyme-linked immunosorbent assay.

We have developed an enzyme-linked immunosorbent assay (ELISA) for the quantitation of C4 nephritic factor (C4NeF). Incubation of the C4NeF-positive serum from patient M.I. with normal human serum (NHS) in the presence of human aggregated IgG (AHG) resulted in the formation of stable C4-C2 complex. No complex was formed in EDTA or under the condition free of AHG. The reaction mixture was filtered through an ACA 22 column, from which the C4-C2 complex was eluted at the first protein peak. When IgG purified from M.I. serum was incubated with NHS and AHG, C4-C2 complex also increased in proportion to dose of the purified M.I. IgG. These results show that C4NeF in M.I. serum stabilizes C4b2a convertase of the classical complement pathway, and is quantified by the ELISA. C4NeF activity was measured, using the ELISA method, in patients with various glomerular diseases, and found elevated in three of 24 patients with membranoproliferative glomerulonephritis (MPGN) type I and slightly but distinctly positive in seven of 24. No C4NeF was detected in two C3 nephritic factor-positive patients with MPGN type II and six with active systemic lupus erythematosus. The new method was more simple and quantitative than C4b2a stabilization assay for C4NeF.

Animals↗
PubMed1980

Nephritic factor of the classical pathway of complement: immunoglobulin G autoantibody directed against the classical pathway C3 convetase enzyme.

A factor, functionally characterized by its capacity to stabilize the normally labile classical pathway C3-converting complex of the classical pathway of complement, has been isolated from the serum of one patient with a case of acute glomerulonephritis, subsequent to a cutaneous infection. The factor confers long-lived stabilization of classical pathway C3 convertase complexes formed both in the solid (sensitized sheep erythrocytes bearing activated C1 and the classical pathway C3 convertase) and fluid phase. The half-life of such stabilized C3-cleaving enzymes extended beyond several hours at 37 degrees C. The stabilizing activity was associated with a protein fraction immunochemically identified as immunoglobulin (Ig)G, a sizeable population of which exhibited a gamma chain of 60,000 daltons. The IgG-associated stabilizing activity was found to bind to the classical pathway C3 convertase enzyme via a fragment bearing the antigen-binding site of the molecule [F(ab)(2) and F(ab)]. Such binding was demonstrable for classical pathway and not for alternative pathway C3 convertase. Thus, the stabilizing factor behaves like an autoantibody to the C3-converting complex of the classical pathway of complement. The binding of the antibody to the enzyme affords protection of the latter against decay-degradation. By analogy with the nephritic factor of the alternative pathway situation where IgG autoantibodies specifically bind to alternative pathway C3 convertase enzymes and protect them from degradation, the functionally unusual IgG in our patient was designated as the nephritic factor of the classical pathway. Indirect evidence suggests that nephritic factor of the classical pathway-IgG might be of the IgG3 subclass.

Adult↗
PubMed1971

Continuing C3 breakdown after bilateral nephrectomy in patients with membrano-proliferative glomerulonephritis.

Serum levels of complement components and of C3 nephritic factor (C3NeF) were measured serially in two patients with membrano-proliferative glomerulonephritis who were subjected to bilateral nephrectomy and maintained by peritoneal dialysis for 2 wk before renal transplantation. In both patients, low levels of C3 and high levels of preformed alpha 2D, a C3 breakdown product, were present before nephrectomy and remained essentially unchanged during the anephric period. With transplantation, C3 levels rose towards normal and alpha 2D disappeared from the serum. The serum of both patients contained detectable amounts of C3NeF, a factor which has been shown to react with a cofactor found in normal serum to form an enzyme, designated C3 lytic nephritic factor (C3LyNeF), which will cleave C3 to form the breakdown products, beta1A and alpha 2D. The level of C3NeF was high in one patient before nephrectomy, increased somewhat during the anephric period, and fell after transplantation. In the other patient, the C3NeF level was initially lower, remained relatively constant during the anephric period, and was not significantly affected by transplantation. In both patients, levels of C4 and C5 were either normal or elevated over the period of the study and bore no relationship to the C3 level. The following conclusions can be drawn from the data. The high levels of alpha 2D during the anephric period and the disappearance of this protein as C3 levels approach normal at the time of transplantation indicate that the low C3 levels were largely the result of C3 breakdown rather than diminished synthesis. The presence of C3NeF in detectable amounts in both patients suggest that C3LyNeF, formed by the reaction of C3NeF and cofactor, was responsible for the low C3 levels. Finally, the lack of effect of nephrectomy on C3, alpha 2D, and C3NeF levels indicate that the site of C3 breakdown was extrarenal and that C3NeF and cofactor are at least in large part of extrarenal origin.

Adolescent↗
PubMed1996

Discordant renal histopathologic findings and complement profiles in membranoproliferative glomerulonephritis type III.

Patients with membranoproliferative glomerulonephritis (MPGN) type III and a low serum C3 concentration tend to have evidence for a nephritic factor of the terminal complement pathway (Nft). Complement profiles were studied in three patients with MPGN type III and low serum C3 concentrations. Serum C3 concentrations were 52, 21, and 14 mg/dL (normal range, 83 to 177 mg/dL). Serum Clq, C2, C4, properdin, and C5 concentrations were normal in all patients, whereas two had a slight decrease of C7 or C8. This pattern of complement activation resembles that seen with MPGN type II in which a nephritic factor activates the amplification loop (NFa). We conclude that in patients with MPGN type III the previously reported profile/presence of Nft is not always found, at least in the chronic stage of the disease, despite a low C3 value.

Biopsy↗
PubMed1989

Mesangiocapillary glomerulonephritis type II (dense-deposit disease): clinical features of progressive disease.

Twenty-seven patients presenting to the Royal Melbourne Hospital between 1968 and 1988 with mesangiocapillary glomerulonephritis type II with intramembranous dense deposits (dense-deposit disease, DDD) are analyzed. Patients were divided into two groups on the basis of whether renal function deteriorated (14 patients) or remained stable (13 patients). At presentation or during the course of the disease, heavy proteinuria, macroscopic hematuria, and high quantitative urinary red cell or white cell counts characterized patients with progressive disease. Patients with crescents on their initial renal biopsy or with large numbers of polymorphs in glomerular capillaries corresponding with sterile pyuria were more likely to have deterioration of renal function. The average time from onset of symptoms to development of end-stage renal disease was over 16 years. The patient's clinical course could not be anticipated by serum complement profiles, the presence of C3 nephritic factor, or partial lipodystrophy. Pregnancy did not affect the course of the disease. Six patients underwent renal transplantation and the disease recurred on renal biopsy in four. However, only two individuals lost renal allografts due to recurrent DDD.

Adolescent↗
PubMed2005

Membranoproliferative glomerulonephritis type II (dense deposit disease): an update.

Membranoproliferative glomerulonephritis type II (MPGN II) is a rare disease characterized by the deposition of abnormal electron-dense material within the glomerular basement membrane of the kidney and often within Bruch's membrane in the eye. The diagnosis is made in most patients between the ages of 5 and 15 yr, and within 10 yr, approximately half progress to end-stage renal disease, occasionally with the late comorbidity of visual impairment. The pathophysiologic basis of MPGN II is associated with the uncontrolled systemic activation of the alternative pathway (AP) of the complement cascade. In most patients, loss of complement regulation is caused by C3 nephritic factor, an autoantibody directed against the C3 convertase of the AP, but in some patients, mutations in the factor H gene have been identified. For the latter patients, plasma replacement therapy prevents renal failure, but for the majority of patients, there is no proven effective treatment. The disease recurs in virtually all renal allografts, and a high percentage of these ultimately fail. The development of molecular diagnostic tools and new therapies directed at controlling the AP of the complement cascade either locally in the kidney or at the systemic level may lead to effective treatments for MPGN II.

Child↗
PubMed1993

Molecular analysis of C3 allotypes in patients with nephritic factor.

The autoantibody nephritic factor (NeF) leads to complement consumption in vivo and is associated with type II mesangiocapillary glomerulonephritis (MCGN II) and partial lipodystrophy (PLD). The third component of complement (C3) exists in two common allotypic forms, C3S and C3F, distinguished at the protein level by electrophoresis. An increased frequency of the rarer C3F allele has been reported in several autoimmune conditions, including one small series of patients with NeF. However, patients with NeF have low levels of circulating C3 so that allotyping at the protein level is difficult. The molecular basis of the S/F polymorphism has recently been established: a single base change at the DNA level encodes a single amino acid substitution at the protein level. A second polymorphism, closely linked to the first, is defined by the MoAb HAV 4-1, and is also due to a single base change. These polymorphisms can therefore be analysed at the DNA level. We have used the amplification refractory mutation system (ARMS), a modification of the polymerase chain reaction (PCR), to analyse these two C3 polymorphisms at the DNA level in 26 patients with NeF. The allele frequencies of C3S and C3F were 0.673 and 0.327 (predicted values 0.79 and 0.2, chi 2 = 4.813, P < 0.05), giving a relative risk of 2.1 for the development of NeF conferred by the presence of a C3F allele. The HAV 4-1 allele frequencies were (-) 0.71 and (+) 0.29, i.e. not significantly different than predicted from the linked C3S/F allele frequencies. This is the largest series of patients with NeF yet published, and our data confirm an association between C3F and NeF. Possible mechanisms for for this link are discussed.

Adolescent↗
PubMed1977

Complement activation in semisolid media: insolubilization of alternative pathway convertases in agar gels with C3 nephritic factor-containing sera.

It was previously shown that when normal human serum and purified properdin or serum containing nephritic factor were allowed to diffuse toward each other in agar, a stainable precipitin line formed only in the presence of an intact alternative pathway. In the present study we have shown that when guinea pig erythrocytes were incorporated in agar and normal human serum was allowed to diffuse toward C3 nephritic factor-containing serum, a line of hemolysis appeared that coincided with the stainable line. The line of hemolysis only formed in the presence of C3, factor B and Mg++, as does the properdin or C3 nephritic factor-induced stainable line. When C2-deficient serum was incorporated in agar with guinea pig erythrocytes and serum samples containing nephritic factor were applied in wells, rings of lysis developed, the areas of which correlated significantly with nephritic factor activity. When partially purified nephritic factor (contaminated only with IgG) or serum containing nephritic factor was subjected to electrophoresis in agar-guinea pig erythrocyte gels and overlaid with normal human serum, bands of lysis developed that required factor B and C3. Lysis of guinea pig erythrocytes in this system appears to be due to insolubilization of alternative pathway convertases with activation of the membrane attack unit C5-C9.

Complement C3↗
PubMed1976

Classical complement pathway activation in membranoproliferative glomerulonephritis.

Levels of components of the classical and alternative complement pathways and the activity of the C3 nephritic factor (C3NeF) were measured in serum specimens from patients with type I (subendothelial deposits) and type II (intramembranous dense deposits) membranoproliferative glomerulonephritis (MPGN) and the results compared with the levels in normal subjects. Although C3 and C5 concentrations were comparably depressed in type I and type II, the levels of Clq and C4 were lower in type I and the correlation coefficients between Clq vs. C4 and C4 vs. C3 were higher than in type II. The profile was highly suggestive of classical pathway activation. In contrast, in type II MPGN, factor B levels were lower and C3NeF activity was more frequently detectable and higher. A feature of interest was that type I, as compared to type II, was characterized by significantly lower serum concentrations of properdin, higher and more significant correlation coefficients between serum properdin concentrations and those of Clq, C4 and C3, and consistent glomerular deposition of properdin. The involvement of properdin in type I may reflect recruitment of a pathway resembling the C1 bypass mechanism, said to involve C1, properdin, factor B and C3-9.

Adult↗
PubMed1976

Serum factors activating the alternative complement pathway in autoimmune disease: description of two different factors from patients with systemic lupus erythematosus.

Serum factors which activated the alternative pathway of complement were detected in 10 of 26 patients with systemic lupus erythematosus (SLE), three of 18 patients with mixed connective tissue disease, one patient with scleroderma, and one with Sjögren's syndrome. This activation was detected by conversion of factor B and C3 into split products and by lysis of glutathione-sensitized human erythrocytes under conditions where classical pathway activation was blocked. The serum factors capable of activating the alternative pathway could be seperated into 7S and 19S-type molecules by sucrose density gradient ultracentrifugation. In two patients with SLE, serum factors were isolated by ion-exchange chromatography, preparative electrophoresis, and molecular sieve chromatography. The serum 7S factor was immunochemically identical to the C3 nephritic factor (C3NeF) of hypocomplementemic chronic glomerulonephritis. Antisera to other complement components failed to react with this purified material. The 7S factor was able to activate the alternative pathway in C2 deficient serum, and in normal human serum under conditions where classical pathway was blocked, but was unable to do so in sera depleted of factor B, factor D, and C3. The activity could be removed by antiserum to C3NeF. In contrast, the serum 19S activator of the alternative pathway was not reactive with antiserum to C3NeF. It had a fast gamma mobility on electrophoresis and the activity could be removed by absorption with anti-IgG and anti-IgM. It was suggested that the 19S factors could consist, in part, of immune complexes.

Absorption↗
PubMed1988

Epstein-Barr virus transformed B cell lines derived from patients with systemic lupus erythematosus produce a nephritic factor of the classical complement pathway.

Nephritic factor of the classical complement pathway (C4NeF) is an IgG antibody which stabilizes the C3 convertase (C4b2a) and has been detected in sera from patients with systemic lupus erythematosus (SLE) and acute postinfectious glomerulonephritis. In order to study the production of nephritic factor (NeF), mononuclear cells were isolated from the peripheral blood of patients with SLE and infected with Epstein-Barr virus (EBV) to establish active B lymphocyte cell lines. Supernatants from 15 established B cell lines, as well as from 10 B cell lines established from normal individuals, were investigated for their ability to conserve the classical and the alternative pathway C3 convertases as assessed by EAC3bBb and EAC14b2a stabilizing assays. Supernatants from 2 of 15 B cell lines from patients with SLE, but none from normal individuals, stabilized the classical C3 convertase without having any effect on the alternative pathway C3 convertase. Using anti-human Ig affinity chromatography, we showed that C4NeF activity resided in the IgG fraction; the IgG fraction containing C4NeF activity bound to the C4b2a complex, but not to C4b alone. On gel electrophoresis, following reduction, the heavy chains were slightly heavier than the heavy chains of normal IgG. We were able to isolate C4NeF from the sera of the 2 patients with SLE from whom the positive supernatants were derived, but were unable to detect any C4NeF activity in the sera of the other 13 patients and the 10 normal individuals. Serum and B cell line supernatant-derived C4NeF exhibited comparable characteristics. We conclude that C4NeF produced in vitro by EBV-transformed B cell lines derived from patients with SLE is functionally similar to the conventional C4NeF in serum. These studies confirm the production of autoantibodies by B cells with the ability to stabilize the classical pathway C3 convertase in certain patients with SLE; stabilization of the C4b2a enzyme in these patients is an apparent mechanism for the development of hypocomplementemia. Finally, preparation of homogeneous C4NeF in vitro should improve our understanding of the role of autoantibodies in complement metabolic disturbances in autoimmune diseases.

Autoantibodies↗
PubMed1980

Dense deposit disease with rapidly progressive renal failure in a narcotic addict.

A girl aged 17 developed a nephrotic syndrome with renal insufficiency after narcotic abuse. Renal biopsy showed a diffuse glomerulonephritis with crescents and dense deposits within the glomerular basement membrane; glomerular C3 deposits were present without immunoglobulin. The serum complement profile was typical of activation via the alternative pathway, and tests for C3 nephritic factor were strongly positive. Terminal renal failure occurred within 6 months and required chronic hemodialysis. It is likely that the narcotics used or their contaminants were responsible for the renal damage, presumably by activating the complement system via the alternative pathway.

Adolescent↗
PubMed1987

Hypocomplementemic glomerulonephritis in an infant and mother. Evidence for an abnormal form of C3.

A mother developed hematuria during the fourth month of pregnancy, and her nursing infant son from this otherwise uncomplicated pregnancy developed hematuria at 3.5 months of age. Both had a mild glomerulonephritis characterized by mesangial prominence, focal thickening and mottling of the glomerular basement membrane and electron-dense deposits, predominantly in the intramembranous and subendothelial positions. Immunofluorescence studies revealed striking accumulations of C3 and other complement components associated with alternative complement pathway activation within glomeruli, and the presence of small or equivocal amounts of immunoglobulin. C1q, C4 and factor B were not detectable. The glomerular lesion was accompanied by hypocomplementemia. Sera of both mother and infant displayed half normal levels of C3 and factor B, increased levels of C4, and normal levels of 12 other complement proteins. High normal or slight elevation in nephritic factor-like activity was observed in serial serum samples. Studies suggested that this mother and son represent the second kindred having an abnormal form of C3 which produces an alternative complement pathway C3 convertase, C3b, Bb, resistant to control by factor H. No additional affected family members were identified. The course of the nephritis over 7 years without drug therapy has been mild with resolving hematuria and no abnormal proteinuria or decrease in creatinine clearance.

Adult↗