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PubMed1979

The complement system in pediatric renal disease.

A brief review of the classical and the alternative pathways of complement activation is presented. Clinically, according to the complement system, we can divide the children with glomerulonephritis into two groups, normocomplementemic and hypocomplementemic. In addition, inherited complement deficiencies can be identified associated with renal diseases. We discuss the three possible sources of complement in urine, although more control studies are necessary in patients with different causes of proteinuria in order to define the clinical significance of complementuria. The immunohistological results of glomerular nephritic biopsy material by the fluorescence antibody technique is analyzed with respect to clinical diagnosis and evaluation of the treatment. The nature of C3NeF as an antibody to factor B-C3 complex is demonstrated by different groups and in different diseases. Finally, the presence of a receptor for complement in the glomerulus, is explained in human disease by the deposition of immune complexes into the renal glomeruli.

Antigen-Antibody Complex↗
PubMed1979

Modulation of the properdin amplification loop in membranoproliferative and other forms of glomerulonephritis.

The mean serum concentrations of C3b inactivator (C3bINA) and beta1H globulin were measured in eighty-six sera (thirty-five membranoproliferative, thirteen membranous, thirty-one focal and seven minimal change) taken from seventy-five patients with histologically diagnosed glomerulonephritis. In none of the four groups of sera did the mean concentrations of both these proteins differ significantly from the mean levels in a group of fifty normal sera. However, in the membranoproliferative group, the mean level of C3bINA, but not beta1H, was significantly lower in the nephritic factor positive than in the nephritic factor negative group. When the eighty-six sera were considered together, serum concentrations of C3bINA and beta1H correlated with levels of C3, factor B, properdin and C4. When the membranoproliferative group was considered separately, C3bINA levels correlated with levels of C3, factor B, properdin and C4 and beta1H correlated with C3 and factor B, but not properdin or C4 in the nephritic factor negative group, but no such correlations were observed in the nephritic factor positive group. The significance of these findings is discussed in the light of current thoughts on the mechanisms of modulation of the alternative pathway.

Beta-Globulins↗
PubMed1983

Characteristics of a benign subtype of dense deposit disease: comparison with the progressive form of this disease.

Pathologic, clinical and serum complement studies were performed on 18 patients with dense deposit disease (DDD). The patients were divided into 3 groups: group A (10 patients who developed end-stage renal failure within 2.9 +/- 1.0 years of onset) group B (3 patients who developed elevated serum creatinines within 6.8 +/- 4.8 years of onset) and group C (5 patients with no evidence of renal insufficiency after 11.0 +/- 1.4 years of follow-up). Renal biopsies from all patients showed intramembranous, electron-dense deposits in glomerular capillary basement membranes. Most group A and B patients presented with a nephritic and/or nephrotic syndrome and followed an active clinical course. In contrast, group C patients presented with either a nephrotic syndrome or asymptomatic proteinuria +/- hematuria and followed a benign course. Sera from group A and B patients contained reduced concentrations of C3 and factor B and large amounts of C3 nephritic factor (NeF) activity. In contrast, serum of group C patients contained normal amounts of C3 and factor B and low levels of C3 NeF activity. These studies show that some patients with DDD (group C) have a benign illness and that they can be identified by serum levels of C3, factor B and C3 NeF activity.

Child↗
PubMed1989

Hypocomplementemic proliferative glomerulonephritis with C3 nephritic-factor-like activity in multiple myeloma.

Advanced renal failure, nephrotic-range proteinuria due to proliferative glomerulonephritis and multiple myeloma with circulating IgG2 lambda and free lambda light-chain paraproteins occurred in a 31-year-old male. Commonly established causes of renal failure in multiple myeloma were excluded. Immunofluorescence revealed heavy granular glomerular deposition of C3. Serum C3 was decreased, and C3c was increased. C3 nephritic-factor (C3 NeF)-like activity was demonstrated in the serum. Plasmapheresis and chemotherapy resulted in a decrease in paraprotein concentration up to 90%, a decrease in C3 NeF-like activity to negligible, normal serum complement levels and a marked improvement in both renal function and proteinuria. With reference to the literature, the possibility of a syndrome of paraproteinemia, C3 NeF-like activity and glomerulonephritis is forwarded.

Adult↗
PubMed1984

C3 metabolism in acute glomerulonephritis: implications for sites of complement activation.

Immunochemical and metabolic studies of complement were performed in 11 patients with acute poststreptococcal glomerulonephritis (AGN) to determine the mechanism(s) of hypocomplementemia. Four patients with profound reduction in serum C3 showed metabolic changes comparable to those seen in hypocomplementemic mesangiocapillary GN (MCGN), that is, nonlinear plasma disappearance of 125I.C3 and a gross (that is, 30-fold) reduction in C3 synthesis (0.01 to 0.02 mg/kg/hr); fractional catabolic rate (FCR) and extravascular/intravascular distribution (EV/IV) ratio were also increased (3.02 to 6.99%/hr; 1.14 to 2.96, respectively). The remaining seven patients had less (or no) reduction in C3 and showed normal or elevated values for all three metabolic parameters; six had linear plasma disappearance curves. Metabolic data in five simultaneously studied control subjects were FCR: 1.56 to 2.12%/hr; EV/IV ratio: 0.12 to 0.41 and synthesis rate: 0.30 to 0.52 mg/kg/hr. C3 nephritic factor (NeF) could not be detected in any sera and a significant reduction in serum C5 accompanied the changes in C3 (r = 0.89; P less than 0.001). Previous studies of C3 NeF-associated MCGN show that the fluid phase alternative pathway convertase seen in this condition has little or no C5 cleaving ability. We propose, therefore, that complement activation in AGN occurs via a surface-bound convertase which is capable of cleaving both C3 and C5. The glomerular capillary could provide such a site for activation.

Adolescent↗
PubMed1986

C3 nephritic factor in an individual with recurrent viral infection and lipodystrophy.

A patient with nephritic factor in the serum following an attack of disseminated herpes is described. In the majority of cases, the factor is associated with mesangio-capillary glomerulonephritis, with or without partial lipodystrophy. It has, however, been described in cases of partial lipodystrophy alone, in one patient with recurrent pyogenic infections, and in one healthy individual. It has not previously been described in an individual with disseminated viral infection.

Adult↗
PubMed1996

Loss of autoantibody activity by alteration in autoantigen.

C3 nephritic factor (C3NeF) is an autoantibody produced by patients with membranoproliferative glomerulonephritis (MPGN); it is thought to be responsible for the continued breakdown of C3 in these patients. We have studied three patients with MPGN for periods of 7 to 17 years who were noted to develop a normal C3 and factor B level in the face of persistent circulating C3NeF. In addition, C3NeF obtained from other sera were inactive when added to these patients' sera. When C3NeF was isolated from these patients' sera, however, it was completely active when added to normal human serum as a source of C3 and factor B. Removal of the C3 and factor B from these patients' sera by passage over anti-C3 and anti-factor B columns followed by reconstitution with C3 and factor B isolated from normal serum allowed C3NeF to be active in these sera. Replacement of C3 alone did not restore activity to these sera but replacement with factor B alone restored full C3NeF activity. These data suggest some alteration in autoantigen (factor B) as a mechanism for reduction in autoantibody (C3NeF) activity.

Adult↗
PubMed1987

[Barraquer and Simons lipodystrophy. Complement anomalies and cutaneous leukocytoclasic vasculitis].

In a 56-year old woman progressive partial lipodystrophy began at the age of 6 years on the face, thereafter extending slowly down to mid-thigh level (fig. 1 and 2), with moderate hypertrophy of the subjacent fatty tissue and a fatty macroglossia (fig. 3). Histological examination of the lipodystrophic skin not only showed an absence of fatty tissue, but also abnormalities at the dermis-epidermis junction with hyaline bodies (fig. 4). At the age of 23 she developed purpura, predominantly on the legs, which rapidly became chronic (fig. 5); histological examination showed leucocytoclasic vasculitis of dermal vessels (fig. 6) with granular deposits of C3 on the vessels and of IgM at the dermis-epidermis junction. Episodes of polyarthralgia and headaches were frequent. Regressive neuritis of the external popliteal nerve occurred when she was 53-year old. Renal function tests proved normal, but renal biopsy was not performed. There was no diabetes mellitus, but an oral glucose tolerance test and a somatostatin insulin glucose test elicited definite resistance to insulin. A search for a serum factor inhibiting insulin receptors was negative. Permanent abnormalities in serum were a very deep fall in C3, a pronounced fall in CH50 and a low C4 level. Besides, a C3 nephritic factor (NeF) at a high level and circulating immune complexes were present (table I); a mixed IgM-IgG cryoglobulin was found intermittently (fig. 7). Clearance of the immune complexes by splenic macrophages was extremely slow. During a series of plasma exchanges, serum C3 increased transiently, whereas serum C4 remained unchanged (fig. 8).(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-Antibody Complex↗
PubMed1988

Interaction between C3 nephritic factor and erythrocyte membranes. Presence of nephritic factor in patients' erythrocytes.

The presence of IgG has been observed by fluorescence microscopy in the erythrocytes of 5 patients with NEF antibody. IgG subclass distribution of the IgG bound was analyzed by fluorescence-activated cell sorter. NEF activity was also determined in the eluted antibodies from the erythrocyte membrane. Three of five patients had NEF antibody bound to the erythrocyte membrane. IgG subclass distribution of NEF antibody sera was also investigated by means of protein A-Sepharose and using monoclonal antibodies against human IgG subclasses. NEF activity was mediated by IgG3 alone in 3 patients and by a combination of IgG1 and IgG3 in 2 patients.

Antibodies↗
PubMed1990

Detection of C3bBb-stabilizing activity (C3 nephritic factor) in the serum from patients with membranoproliferative glomerulonephritis.

It is known that membranoproliferative glomerulonephritis (MPGN), hypocomplementaemia and C3 nephritic factor (C3NeF) are closely related to each other, and the presence or absence of C3NeF in the serum is important for evaluating the nature of MPGN. However, some difficulties have been encountered in detecting this factor and therefore a new assay permitting the direct detection of C3NeF without purifying IgG from the patient's serum has been devised. Using this assay method, C3bBb-stabilizing activity was observed even in sera from MPGN patients who were non-hypocomplementaemic. Furthermore, among 98 cases with hypocomplementaemia. C3NeF was found to be absent in 66 cases.

Complement C3 Convertase, Alternative Pathway↗
PubMed1991

Familial incidence of C3 nephritic factor.

C3 nephritic factor (NEF) has been found in 3 siblings presenting different (or none) degrees of renal disease. Other relatives, including their dead father, suffered from a renal illness. In 2 of the siblings, NEF activity was restricted to IgG1 and IgG3 subclasses. Familial NEF incidence and a shared C3 allotype and a common HLA haplotype including BfS alleles for the 3 NEF-positive siblings suggest that at least in our cases genetical factors may be involved in NEF generation.

Adolescent↗
PubMed1979

[Complement and nephritic activity in membranoproliferative glomerulonephritis].

A study of complement profiles and of "nephritic activity" (NeF activity) has been carried out in 33 children presenting with membranoproliferative glomerulonephritis (MPGN), in order to determine the pathway of complement activation. By morphological studies two varieties of MPGN have been distinguished. In MPGN with subendothelial deposits, immunofluorescent studies and complement profiles show an activation by the classical pathway. The demonstration of NeF activity in 7 of 20 patients suggests that there is recruitment of the amplification pathway. In MPGN with dense deposits, immunopathological studies indicate an activation of the complement system through the alternate pathway, NeF activity being present in 10 of 13 patients. With the functional tests used, it is not possible to ascertain that the factors responsible for the NeF activity in MPGN with subendothelial deposits are identical to the C3NeF identified in MPGN with dense deposits and/or partial lipodystrophy.

Capillaries↗
PubMed1989

C3 nephritic factor and C4 nephritic factor in the serum of two patients with hypocomplementaemic membranoproliferative glomerulonephritis.

Both C3 nephritic factor (C3NeF) and C4 nephritic factor (C4NeF) were found in the serum of two patients with hypocomplementaemic membranoproliferative glomerulonephritis type 1 (H-MPGN type 1). Both stabilizing activities were associated with the IgG fraction. The serum levels of C3 and C5 were quite low, whereas the levels of early components and control proteins were in the normal range.

Adolescent↗
PubMed1981

'Nephritic factor' may be an autoantibody to C3b or C4b.

We attempted to clarify the character of 'Nephritic Factor' in the alternative (NeFA) and classical pathways (NeFC) of the complement, using an agglutinating and a hemolytic activity assay. The results suggested a possibility that NeFA and NeFC were different in their ability but might appear at the same time in some cases, and that NeFA was anti-C3b autoantibody and NeFC anti-C4b autoantibody.

Autoantibodies↗
PubMed1993

Complement-mediated adipocyte lysis by nephritic factor sera.

Recent data indicate a previously unsuspected link between the complement system and adipocyte biology. Murine adipocytes produce key components of the alternative pathway of complement and are able to activate this pathway. This suggested to us an explanation for adipose tissue loss in partial lipodystrophy, a rare human condition usually associated with the immunoglobulin G(IgG) autoantibody nephritic factor (NeF) which leads to enhanced alternative pathway activation in vivo. We hypothesized that in the presence of NeF, there is dysregulated complement activation at the membrane of the adipocyte, leading to adipocyte lysis. Here we show that adipocytes explanted from rat epididymal fat pads are lysed by NeF-containing sera but not by control sera. A similar pattern is seen with IgG fractions of these sera. Adipocyte lysis in the presence of NeF is associated with the generation of fluid-phase terminal complement complexes, the level of which correlates closely with the level of lactate dehydrogenase, a marker of cell lysis. Lysis is abolished by ethylenediaminetetraacetic acid, which chelates divalent cations and prevents complement activation, and reduced by an antibody to factor D, a key component of the alternative pathway. These data provide an explanation for the previously obscure link between NeF and fat cell damage.

Adipose Tissue↗
PubMed1985

A new and specific enzyme-linked immunosorbent assay for the detection of C3 nephritic factor.

C3 nephritic factor (C3 NeF) was measured by assessing its capacity to form complex with C3 and B using an enzyme-linked immunosorbent assay (ELISA). Incubation of C3 NeF with normal human serum in the presence of MgEGTA resulted in a dose-dependent increase of C3-B-IgG complex. No complex was formed in EDTA. The C3 NeF titer estimated in this way was in good accordance with those reported previously by other indirect methods.

Complement C3↗