Pathogenesis and approaches to therapy of membranoproliferative glomerulonephritis

C3 glomerulopathy and current dilemmas

C3 glomerulopathy (C3G) is a recently identified disease entity caused by dysregulation of the alternative complement pathway, and dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) are its components. Because laboratory detection of complement dysregulation is still uncommon in practice, "dominant C3 deposition by two orders greater than that of immunoglobulins in the glomeruli by immunofluorescence", as stated in the consensus report, defines C3G. However, this morphological definition possibly includes the cases with glomerular diseases of different mechanisms such as post-infectious glomerulonephritis. In addition, the differential diagnosis between DDD and C3GN is often difficult because the distinction between these two diseases is based solely on electron microscopic features. Recent molecular and genetic advances provide information to characterize C3G. Some C3G cases are found with genetic abnormalities in complement regulatory factors, but majority of cases seem to be associated with acquired factors that dysregulate the alternative complement pathway. Because clinical courses and prognoses among glomerular diseases with dominant C3 deposition differ, further understanding the background mechanism, particularly complement dysregulation in C3G, is needed. This may resolve current dilemmas in practice and shed light on novel targeted therapies to remedy the dysregulated alternative complement pathway in C3G.

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.

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.

Prednisone therapy of membranoproliferative glomerulonephritis in children

Six children with biopsy-proved type 1 membranoproliferative glomerulonephritis (MPGN) improved clinically during a 2-year course of prednisone therapy. All children had nephrotic syndrome. Creatinine clearance was less than or equal to 80 ml/min/1.73 m2 in four patients. Initial prednisone dosage ranged from 20 mg every other day to 2 mg/kg/day (maximum 60 mg), with subsequent modifications based on improvement. After completion of a 2-year course of steroid therapy, a repeat kidney biopsy was performed in each child; a decrease in glomerular disease activity was noted in five of them. After a mean follow-up of almost 5 years, all children have creatinine clearance greater than 120 ml/min/1.73 m2, and only one remains nephrotic. Although the use of prednisone in children with MPGN remains controversial, we have observed a diminution in proteinuria and normalization of creatinine clearance with therapy initiated early in the disease course.

Dense deposit disease in children: prognostic value of clinical and pathologic indicators. The Southwest Pediatric Nephrology Study Group

Clinical and pathological features were examined in 16 children with dense deposit disease. The children ranged in age from 5 to 15 years (mean: 9.3 years). There were nine boys and seven girls. Semiquantitative grading of renal biopsy findings was performed in these patients and compared to clinical features at the time of presentation, and at the time of latest follow-up. Initial clinical features included hypertension and decreased glomerular filtration rate in 50% of patients, nephrotic syndrome in 69%, and gross hematuria in 73%. Serum C3 concentrations were low in nine of nine patients. All but one of the patients subsequently received steroid therapy, the dosage of which varied. Of the 16 patients, six developed progressive renal insufficiency, six have normal renal function after a period of 7 to 12 years, and four have normal renal function but have been followed for less than 6 years. When these different subgroups were compared, clinical and laboratory features were not helpful outcome indicators. By contrast, poor outcome was correlated with the following pathologic features: excessive prominence of glomerular lobules, severe mesangial hypercellularity and sclerosis, severe glomerular loop obliteration, and mesangial electron dense deposit alteration. We conclude that the course of dense deposit disease is variable and that certain pathologic features may be helpful in predicting clinical outcome. Whether alternate-day prednisone therapy may have been of benefit for the patients in this study is uncertain.

Results of a controlled drug trial in membranoproliferative glomerulonephritis

A prospective randomized drug trial was carried out on 59 patients with confirmed membranoproliferative glomerulonephritis (MPGN). The treatment group (27 patients) received cyclophosphamide, coumadin, and dipyridamole for 18 months, and the control group (32 patients) received no specific therapy. Complications of the renal disease such as hypertension and fluid retention were treated similarly in both groups. Entrance criteria included confirmed renal pathology demonstrating either types I or II MPGN, a corrected creatinine clearance (CCr) of less than 80 ml/min/1.73 m2, and/or proteinuria greater than 2 g/day. Actuarial survival was not different between the treatment and the control groups in either MPGN type and was 85% in type I and 90% in type II at 2 years. The change in renal function, as measured by both the slope of CCr and the plasma creatinine reciprocal (1/Cr) at 6, 12, and 18 months was not significantly different between treatment and control groups in either types I or II when tested by both parametric and nonparametric analysis. The age, sex, and initial level of CCr did not influence the rate of decline. Control and treatment group proteinuria was not different at any time point in either types I or II MPGN. The small numbers of type II MPGN cases do not give sufficient power to allow conclusions regarding this therapy in type II. We can conclude that this treatment is ineffective in altering the natural history of type I MPGN.

Glomerulonephritis with dense deposits: a variant of membranoproliferative glomerulonephritis or a separate morphological entity? Light, electron microscopic and immunohistochemical study of eleven cases

Eleven cases of glomerulonephritis with dense deposits were selected on the basis of electron microscopic examination performed either on material treated according to conventional techniques (9 cases) or on previously paraffin-embedded material (2 cases). While uniform immunohistochemical patterns were observed, different features were shown by light microscopy: in only 3 cases were membranoproliferative or lobular patterns present, while in the others a varying degree of mesangial cell proliferation (moderate, mild or even very scanty with focal and segmental distribution) was detected. The generally accepted statement that glomerulonephritis with dense deposits represents a subgroup of membranoproliferative glomerulonephritis therefore seems questionable. In addition to several clinical and serological data, these morphological features give further support to the hypothesis that glomerulonephritis with dense deposits in all respects a peculiar and distinct form of glomerulonephritis.

Control of complement activation in membranous and membranoproliferative glomerulonephritis

Renal biopsy specimens from 22 membranous (MGN) and 19 membranoproliferative glomerulonephritis (MPGN) patients were examined for the presence of the three regulators of the complement system; C1- inhibitor (C1--INH), C3b inactivator (C3b-INA), and beta 1H. The serum concentrations of these proteins, at the time of biopsy, were also measured. To study the modulation of complement activation by these three control proteins in MGN and MPGN, we examined the relationship between each control protein and the protein whose activity it regulates, in four ways; (a) the concordance between the presence of the control proteins and the components regulated was studied, (b) the correlations in intensity of deposition of the control and complement proteins were measured, (c) the patterns of distribution of the proteins within the glomeruli were compared, and (d) the serum levels of control proteins and components, regulated were examined. C1--INH (23 of 35 biopsies) and beta 1H (34 of 36 biopsies) were frequently deposited in both disease groups. C3b-INA was found only rarely in MPGN (4 of 19 biopsies). This is probably because the former two proteins modulate complement activation stoichiometrically, whereas C3b-INA acts enzymatically. A relationship was demonstrated between C1--INH and C1s and between beta 1H and C3 in both groups, but no such relationship was found between C3bINA and C3. Conclusion. There is no generalized deficiency in modulation of complement activation in MGN or MPGN.

Idiopathic rapidly progressive glomerulonephritis with C3 nephritic factor and hypocomplementemia

A 7-year-old boy with mild renal failure and signs and symptoms of acute poststreptococcal glomerulonephritis including severe hypocomplementemia had, by renal biopsy, numerous crescents but no deposits in the glomerular capillary loops. Instead, deposits identical in location and composition to those described for children with idiopathic rapidly progressive glomerulonephritis were present. The severe hypocomplementemia was found to be due to high levels of C3 nephritic factor; niether nephritic factor nor hypocomplementemia has been reported in rapidly progressive glomerulonephritis of the idiopathic type. Following prompt therapy with methylprednisolone intravenously, serologic abnormalities disappeared and renal function greatly improved, but a later biopsy showed 50% of the glomeruli obliterated by scarring. The case is of importance not only in indicating that severe hypocomplementemia does not rule out idiopathic rapidly progressive glomerulonephritis but also in adding to the list of diseases in which nephritic factor can be found.

Renal artery dysplasia in a patient with membranoproliferative glomerulonephritis

A 27 year old man with nephrotic syndrome due to membranoproliferative glomerulonephritis had multifocal stenoses of the renal and intestinal arteries. The arterial lesions demonstrated by angiograhy closely resembled those of medial fibromuscular dysplasia. The dysplasia progressed over a five year period to involve both renal arteries from their extrarenal segments through their interlobar branches. Low serum levels of complement components C3 and C4, focal reduplication of the glomerular basement membrane on light microscopy, and the patterns of glomerular localization of IgG and C3 by immunofluorescence were characteristic of type I membranoproliferative glomerulonephritis. The development of the arterial dysplasia in a patient with chronic glomerulonephritis suggests a common immunologic pathogenesis of both disorders.

Immune complex glomerulonephritis in sicca syndrome

In three patients with the sicca syndrome (Sjögren's syndrome), who were followed for one to seven years, glomerulonephritis developed. None of these patients fulfilled the diagnostic criteria for systemic lupus erythematosus. All of these patients had circulating immune complexes as detected by the Clq binding assay. Glomerular histology by light and electron microscopy revealed changes compatible with membranoproliferative glomerulonephritis in two of the patients and membranous glomerulonephritis in the third. All patients showed rapid improvement in renal function following moderate doses of corticosteroids. In addition, the treatment decreased the level of circulating immune complexes in two patients who were followed for a sufficient period of time.

Recurrent dense deposit disease in renal allograft

This report documents the recurrence of dense deposit disease in a renal allograft thirty-three days post-transplantation and stresses the usefulness of immunofluorescence in early detection.

Severe glomerulonephritis complicated by coagulopathy: treatment with anticoaguland and immunosuppresive drugs

Serial determinations, using plasma fibrinogen gel chromatography as well as standard methodology, demonstrated that six children with severe glomerulonephritis, characterized on renal biopsy by glomerular necrosis and crescent formation, had persistent evidence of intravascular coagulation. Based on these observations, therapy with anticoagulants and azathicoagulants and azathioprine was instituted for one year; treatment with anticoagulants was continued for a second year. Anticoagulant therapy was initiated with heparin, followed by oral anticoagulation with phenindione and dipyridamole. In contrast to our earlier experience with similar patients, each of the present patients improved. Urinalyses returned to normal and glomerular filtration rates to near normal values in all patients at the end of the treatment period and have remained so for up to 3.9 years since treatment has been completed. Post-treatment biopsies showed remarkable improvement, with virtually no glomerulosclerosis even in patients who had had a high incidence of glomerular crescents before treatment. It is suggested that the therapeutic regimen favorably influenced the natural history of disease and that plasma fibrinogen chromatographic findings may be helpful in selecting patients likely to benefit from the use of anticoagulant therapy.

Nephritic factor: Description of a new quantitative assay and findings in glomerulonephritis

A sensitive quantitative test for nephritic factor (NF) in human serum is reported. The test is based on the capacity of NF to initiate fluid phase consumption of the third complement (C) component in the presence of magnesium ions (Mg++) and of factors of the alternative pathway of C activation. These factors as well as C3 and C5 were supplied by the incorporation of normal human serum (NHS) into the assay mixture. In order to prevent C3 (and C5) consumption via the Ca++- and Mg++-dependent classical pathway, the test was performed in the presence of the chelating agent Mg-ethylene bis (oxyethylene-nitrilo) tetraacetic acid (Mg EGTA) which interacts preferentially with Ca++. The Mg EGTA concentration was found to be critical, a final concentration of 5 mM in the assay mixture being required for optimal results. By its heat stability (54 degrees to 56 degrees C, 30 min), NF could be distinguished from other, heat-labile NF-like factors. The NF test was applied to five categories of patients with glomerulonephritis (GN). Heat-stable NF activity was found in seven of 17 sera in the membranoproliferative glomerulonephritis (MPGN) group. Two of the 12 acute poststreptococcal GN sera had NF-like activity which disappeared upon heating. Serum C3 and proactivator (PA) concentrations varied widely in all groups but a clear positive relationship was found between the presence of NF and low serum C3 concentrations in MPGN. Renal immunofluorescence in MPGN indicated a lesser amount of lg deposited in glomeruli from patients with NF when compared to the NF-negative patients. Both groups had heavy C3 deposits. The availability of a sensitive, quantitative assay for NF may help to provide further insight into the various pathogenic mechanisms in different forms of MPGN.