Plasma terminal complement complexes in acute poststreptococcal glomerulonephritis

In most instances of acute poststreptococcal glomerulonephritis (APSGN), activation of the complement system occurs, as reflected by decreased levels of the complement proteins C3, C5, and properdin (P). Recent studies implicate terminal complement complexes (TCC) in the pathogenesis of glomerular injury. The fluid phase TCC, SC5b-9, reflects the formation of membrane-bound C5b-9 and has been used as a clinical marker in various diseases. Plasma concentrations of SC5b-9 were measured with an enzyme immunoassay using a monoclonal antibody to a neoantigen expressed on the SC5b-9 complex in 13 children who presented with clinical and pathologic features of APSGN. SC5b-9 was significantly elevated in all plasmas obtained within 30 days after onset of clinical glomerulonephritis. Concentrations of SC5b-9 in acute plasmas were significantly higher than those of paired convalescent samples. For individual patients, as SC5b-9 concentration returned to normal there was a coincident decrease in serum creatinine concentration and urinary protein excretion, signifying clinical improvement in glomerulonephritis. Thus, TCC generation commonly occurs in the early stages of APSGN and may be of importance in the pathogenesis of the condition.     

Clinical significance of the terminal complement complex in children with type I membranoproliferative glomerulonephritis

We measured the concentrations of terminal complement complex (TCC) in plasma (n =25) and urine (n=13) using an enzyme-linked immunosorbent assay in pediatric patients with type I membranoproliferative glomerulonephritis(MPGN). Frozen tissue from 18 renal biopsies was evaluated for the presence of TCC by direct immunoperoxidase staining. In the acute phase of the disease, TCC concentrations in plasma were elevated above 0.5 AU/ml in 14 of 25 patients (High TCC group), while the remaining 11 patients showed less than 0.5 AU/ml (Low TCC group). In the High TCC group, TCC was deposited more diffusely and intensely in the glomerulus, compared to that in the Low TCC group (p= 0.034). Furthermore, urinary TCC concentrations in the High TCC group were higher than those in the Low TCC group (p=0.0001). The High TCC group showed not only a poorer response to steroid treatment, but also a poorer prognosis than the Low TCC group. These results suggest that, in pediatric patients with type I MPGN, TCC in circulation may play a certain role in TCC formation in the glomerulus and in urine. The TCC concentration in plasma could be used as a marker of responsiveness to steroid treatment and long-term prognosis.     

Changes of complement in immune complex glomerulonephritis induced by cationized antigen

Complement system takes an important role in the pathogenesis of immune complex glomerulonephritis. In this study the precise changes of serum complement and its deposition in the glomeruli were investigated in the mice models induced with cationized bovine gamma-globulin (CBGG). Balb/c mice preimmunized with CBGG were injected intravenously with CBGG three times every 24 hours. Proteinuria and hypoalbuminemia have developed from day 3 until the death on day 9-13 of progressed azotemia. This nephritis resembled to mesangial proliferative glomerulonephritis histopathologically. Immunofluorescent study revealed granular deposits of CBGG, IgG, A, M and C3 along the glomerular capillary loop. Serum C3 decreased to about 50% of normal controls within 1 hour after challenge of antigen and plasma C3 conversion evaluated by crossed-immunoelectrophoresis, occurred in accordance with C3 reduction and then decreased. Immunofluorescent study showed a big difference in the mode of deposition among IgG, CBGG and C3. The most intense deposits of C3 in the glomeruli were seen 12 hours after challenge of CBGG, and then gradually decreased until the next challenge. IgG and CBGG antigen deposited most intensely soon after the challenge of antigen, and gradually decreased. These results led us to conclude that there existed two phases of complement activation in this immune complex induced mice glomerulonephritis; an early phase activation of complement by antigen-antibody complexes in the circulation and later phase activation of complement by immune complexes after deposition of them in situ glomeruli.     

Terminal complement complexes in acute poststreptococcal glomerulonephritis

Activation of the complement cascade occurs in most cases of acute poststreptococcal glomerulonephritis (APSGN) and results in the formation of the terminal complement complexes (TCC). To examine the possible role of TCC in the pathogenesis of glomerular injury in APSGN, we studied 30 patients with the clinical diagnosis of APSGN. All patients had an elevated plasma SC5b-9 concentration at the onset of clinical nephritis. Serial plasma concentrations showed an inverse linear relationship with time after onset of clinical disease (r=–0.59,P=0.0008), while plasma C3 concentrations showed a positive linear relationship (r=0.78,P=0.0001). Renal biopsies of 5 patients demonstrated co-localization of C5b-9, S-protein, and C3 deposition in a glomerular capillary loop and mesangial distribution. Urinary excretion of TCC in the acute phase of APSGN was not elevated and was not a useful marker of disease activity. These data suggest that in APSGN with terminal complement pathway activation the local generation of TCC may contribute to the pathogenesis of the disease.     

Anaphylatoxins and terminal complement complexes in pancreatitis. Evidence of complement activation in plasma and ascites fluid of patients with acute pancreatitis

Complement activation has been proposed as a mediator of remote complications of acute pancreatitis. Thirty-seven patients with acute pancreatitis were studied with respect to the formation of anaphylatoxins (C3a/C3adesArg, C5a/C5adesArg) and terminal complement complexes (TCC) in plasma and ascites fluid. The patients were classified according to Ranson's criteria. Eighteen patients with moderate or severe pancreatitis had higher maximum plasma C3a/C3adesArg and TCC concentrations than 19 patients with mild pancreatitis. During convalescence, the concentrations had returned to normal. High concentrations of C5a/C5adesArg and TCC were also found in ascites and pancreatic cyst fluid, drawn from patients with moderate or severe pancreatitis. As the terminal complement pathway activation is involved in reactive lysis and anaphylatoxins increase vascular permeability, anemia and impaired respiration in these patients may be influenced by complement activation.     

Circulating immune complexes and complement breakdown products in childhood IgA nephropathy]

Circulating immune complexes (CIC), mainly IgA-CIC have been frequently detected in IgA nephropathy and recently increased levels of C3 fragments which indicate C3 activation have been reported. However, little is known about the relationship between CIC and complement activation. We determined CIC by the solid-phase anti-C3 Facb enzyme immunoassay in 37 children with IgA nephropathy to investigate the relationship between CIC and clinical and/or histological findings, and also determined C3 fragments whether CIC correlate with complement activation. IgA-CIC were detected in 78% (27/37) with a mean level of 11.9 +/- 3.9 micrograms/ml, which was significantly higher than other glomerular diseases (P less than 0.05). IgA-CIC levels were also found significantly higher in 27 cases with proteinuria than in 10 cases without proteinuria (P less than 0.05). IgG-CIC were detected in 67% (12/18) with a mean level of 4.1 +/- 2.6 micrograms/ml, which was not significantly different from other glomerular diseases. No striking correlation was noted to exist between CIC levels at renal biopsy and the histological severity, because CIC are often present intermittently. C3d was quantitated by the rocket immunoelectrophoresis and C3 by the single radial immunodiffusion to determine the C3d/C3 ratio. The mean value of C3d/C3 was 0.63 +/- 0.19 which was significantly higher than a corresponding value for 15 healthy controls of 0.27 +/- 0.06 (P less than 0.05). Levels of IgA-CIC were found to have a significant positive correlation between C3d/C3 determined simultaneously in 33 cases (r = 0.43, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Mesangial immune complex glomerulonephritis due to complement factor D deficiency

Complement factor D is a serine protease essential for the activation of the alternative pathway and is expressed in the kidney, adipocytes, and macrophages. Factor D is found at relatively high levels in glomeruli suggesting that this component of the complement cascade could influence renal pathophysiology. In this study, we utilize mice with a targeted deletion of the activating complement factor D gene and compare these results to mice with targeted deletion of the inhibitory complement factor H gene. Eight-month-old mice with a deleted factor D gene spontaneously develop albuminuria and have reduced creatinine clearance due to mesangial immune complex glomerulonephritis. These mesangial deposits contain C3 and IgM. In contrast to the mesangial location of the immune deposits in the factor D-deficient mice, age-matched factor H-deficient mice develop immune deposits along the glomerular capillary wall. Our observations suggest that complement factor D or alternative pathway activation is needed to prevent spontaneous accumulation of C3 and IgM deposits within the mesangium. Our studies show that the complement factor D gene knockout mice are a novel model of spontaneous mesangial immune complex glomerulonephritis.     

Possible involvement of terminal complement complex in active Heymann nephritis

We investigated whether the appearance of various complement components in renal deposits of immune complexes correlated with the development of proteinuria in rats with active Heymann nephritis. Sequential kidney biopsy specimens and serum samples were obtained from Lewis rats immunized with Fx1A in complete Freund's adjuvant. Circulating antibodies against purified auto-antigen renal tubular epithelial glycoprotein, as measured by ELISA, were found in the circulation together with a diffuse granular deposition of IgG1, IgG2a, and IgG2b in the glomeruli within 2 weeks after immunization. Biopsy specimens taken 4 weeks after immunization showed diffuse deposition of C4 and C3, which indicated that activation of complement by the classical pathway had occurred. The detection of the C5b-9 complex of complement in glomerular deposits coincided with the development of abnormal proteinuria indicating that the glomerular damage in this autoimmune disease may be caused by complement-mediated lesions in the glomerular capillary walls.     

Immunohistochemical analysis of C3 cleavage fragments, factor H, and the C5b-9 terminal complex of complement in de novo membranous glomerulonephritis occurring in patients with renal transplant

Fifteen renal biopsies from 13 transplanted patients with de novo membranous nephropathy (DNMN) were investigated by immunofluorescence for the presence of C5b-9 neoantigens of the terminal sequence of complement and for antigens expressed by C3 cleavage fragments. DNMN lesions were classified as stage I, II or III upon light and electron microscopy examination. Seven biopsies were classified as stage I DNMN and 8 stage II-III. All patients were proteinuric. In six biopsies with stage I DNMN, staining for C5b-9 neoantigens was restricted to a fine granular labeling in mesangial areas which was analogous to that seen in normal kidneys in contrast with extensive parietal labeling for IgG, C3d and factor H antigens. In eight biopsies with stage II-III DNMN, the pattern of staining with anti-C5b-9 neoantigens antibodies was similar to that obtained with anti-IgG, anti-C3d and anti-factor H antibodies. These results suggest that in situ activation of the whole complement sequence throughout C5b-9 only occurs on large immune deposits (stage II-III DNMN).     

Medium- and long-term prognosis of patients with acute poststreptococcal glomerulonephritis

The prognosis of acute poststreptococcal glomerulonephritis (APSGN) is still a matter of considerable debate. In an attempt to elucidate this controversy, the medium-term prognosis was evaluated in 40 patients 5-9 years after the onset of the disease, and the long-term prognosis in 88 patients 10-17 years after the onset of the disease. All were sporadic cases. In the medium-term follow-up study, abnormalities were revealed in 5.0% (2/40) of the patients. Hypertension and proteinuria were the only abnormalities detected. In the long-term follow-up study, abnormalities were revealed in 6.8% (6/88) of the patients. Hypertension was found in 3.4, proteinuria in 2.3, and microhaematuria in 2.3% of the patients. In both studies, all patients had normal creatinine clearance. We conclude that the medium- and long-term outcome of patients with APSGN is excellent.     

Clinical evaluation and characterization of a unique C3 breakdown factor detected in a patient with acute glomerulonephritis

A unique factor causing breakdown of the third component of complement (C3) was detected in a patient with acute glomerulonephritis (AGN). The activity was detected by conversion of C3 in a mixture with normal human serum using crossed immunoelectrophoresis. This factor capable of C3 breakdown was not blocked in the presence of ethylenediaminetetraacetic acid (EDTA), heat-pretreatment (56 degrees C, 30 min) und dialysis against 0.1 M phenylmethylsulfonyl fluoride (PMSF). The factor was isolated and characterized by immunochemical and physicochemical techniques. It had beta-mobility on electrophoresis and was separated at a lighter sedimentation coefficient than 7S by sucrose density gradient ultracentrifugation. The activity was absorbed on a DEAE-cellulose column and was eluted under definite conditions of relative salt concentration. These data appear to suggest that this factor is distinct from C3 nephritic factor (C3NeF), immunoglobulins, immune complexes, and other C3 convertases previously described. Moreover, it is clear that the factor was mainly responsible for the C3 activation observed in the patient with acute glomerulonephritis.     

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.     

Clinicopathological features and prognosis of Chinese patients with acute post-streptococcal glomerulonephritis

Aim: To investigate clinicopathological and prognostic differences between adults and children with acute post‐streptococcal glomerulonephritis (APSGN). Methods: A retrospective case series of 112 patients with APSGN was undertaken. Patients were divided into two groups according to age: adults aged more than 17 years and children aged less than 15 years. Results: The incidence of APSGN, especially in adults, has decreased in the past three decades. Children have had a higher incidence of macroscopic haematuria than adults (58.3% vs 32.7%, P < 0.05). Laboratory test showed that red blood cell count of urine sediment in children was more significant. On light microscopy, adults had more global glomerulosclerosis, tubular basement membrane thickening, tubular atrophy and interstitial fibrosis, while children had more glomerular infiltrating neutrophils and monocytes and cellular casts. Immunofluorescence microscopy showed that classical staining was seen more in children. The short‐term prognoses were good in both children and adults. But the recovery rate of proteinuria in children was faster than that in adults. Conclusion: Adults with APSGN had similar clinical features as children except that children had more significant haematuria. On pathology, adults had more outstanding chronic changes by light microscopy and more untypical staining by immunofluorescence.     

Membranoproliferative glomerulonephritis with C3NeF and genetic complement dysregulation

The development of membranoproliferative glomerulonephritis (MPGN) is associated with uncontrolled activation of the complement alternative pathway. This dysregulation is related either to C3 nephritic factor (C3NeF), an auto-antibody directed against the alternative C3 convertase, or to homozygous loss-of-function mutation of the complement regulatory protein factor H. Heterozygous mutations in the genes coding for factor H, or for the other alternative pathway inhibitory proteins factor I and membrane cofactor protein, have recently been identified in a small number of patients with MPGN with exclusive C3 deposits. We report three hypocomplementemic children with dense deposit disease (n = 1) or immune-complex-mediated MPGN type I (n = 2), associated with both C3NeF activity and heterozygous mutation of factor H or factor I. These observations highlight the possible combination of genetic and acquired defect in complement control in various subtypes of MPGN, a finding that may influence the treatment strategy in some patients.     

Incidence of circulating immune complexes in patients with acute poststreptococcal glomerulonephritis and in patients with streptococcal impetigo

In an attempt to further study the possible contribution of circulating immune complexes (CIC) in the pathogenesis of acute poststreptococcal glomerulonephritis, 61 patients with APSGN were studied during the first three weeks of the disease, and 13 patients with noncomplicated streptococcal impetigo as a control group. C1q solid phase ELISA and Conglutinin (K) solid phase ELISA were used to measure the levels of immune complexes. The incidence of CIC in a single serum sample from patients with APSGN was 48%. Elevated levels of immune complexes were found in 46% of the patients with streptococcal impetigo. The absolute levels of CIC were comparable in both groups of patients. No correlation was found among the presence of CIC and the clinical, immunoserological or pathological findings of the disease. Our results do not support the hypothesis that trapping of the circulating immune complexes play an important role on the renal injury poststreptococcal infection. Instead, we suggest that CIC are an epiphenomena present in APSGN, and may represent rather a systemic inflammatory immune response in patients with group A streptococcal infection.     

Inherited complement component deficiencies in membranoproliferative glomerulonephritis

Anecdotal reports of complement component deficiencies in patients with immune complex disease led to a systematic study of the levels of seven complement components in serum specimens from 178 patients with glomerulonephritis and 163 normal subjects. Deficiencies were found with significantly higher frequency (22.7%) among 44 patients with membranoproliferative glomerulonephritis (MPGN) types I and III, than among the normal subjects (6.7%, P less than 0.002) or among 134 patients with other glomerulonephritides (5.2%, P less than 0.001). The component deficiencies in MPGN were partial in nine patients and subtotal in one. They could not be ascribed to acquired hypocomplementemia or to a nephrotic syndrome. They were present over long periods, were found in family members, and involved C2, C3, factor B, C6, C7, and C8. Six were presumably the result of null structural genes, two were associated with a structurally abnormal component, and two were of unknown cause. The results give evidence that partial deficiency of one or more complement components is a factor predisposing to MPGN.