Terminal complement complexes in childhood type I membranoproliferative glomerulonephritis

BACKGROUND: The role of terminal complement complexes (TCCs), which are the final products of complement activation, in the pathogenesis of human glomerulonephritis has not been completely elucidated. To clarify the clinical significance of TCCs in type I membranoproliferative glomerulonephritis (MPGN), we studied TCCs in plasma, renal tissue and urine in pediatric patients with this disease. PATIENTS AND METHODS: We measured the concentrations of TCC in plasma (n=25) and urine (n=13) using enzyme-linked immunosorbent assay. Frozen tissue from 18 renal biopsies were evaluated for the presence of TCC by direct immu-noperoxidase staining. RESULTS: At the early stage of the disease, TCC concentrations in plasma were elevated to above 0.5 arbitrary units (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, TCCs were deposited more diffusely and intensely in the glomerulus, compared with those 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 poorer prognosis than the low-TCC group. CONCLUSIONS: These results suggest that, in pediatric patients with type I MPGN, TCCs in circulation may play a particular 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.     

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.     

Pathways of complement activation in membranoproliferative glomerulonephritis and allograft rejection.

The complement system is comprised of at least 18 plasma proteins and consists of four functional divisions: two pathways for activation (classical and alternative), a common amplification mechanism for the activating pathways, and a final common effector pathway to which the activating and amplifying sequences are directed. The classical pathway is activated by certain antigen-antibody complexes, while the alternative pathway may be initiated non-immunologically by various microbial polysaccharides. Indeed, mixtures of purified C3, B, D, and P regulated to low-grade interaction by the presence of C3bINA and beta1 H respond to zymosan with amplified C3 and B inactivation. Both pathways form enzymes termed C3 convertases that cleave C3 to generate its major fragment, C3b. C3b interacts with each C3 convertase to permit C5 cleavage in activation of the effector complement sequence, and it interacts with alternative-pathway factors B and D to generate additional C3 convertase, C3bBb, in the amplification pathway. As C3 cleavage represents the most critical step in the elaboration of the biologic effects of the complement system, modulation of this reaction by generation, stabilization, and inactivation of the amplification convertase C3bBb may well determine whether initial activation of the complement sequence eventuates in beneficial or detrimental effects for the host. Initial generation of C3bBb is dependent on prior cleavage of C3, which may occur by the classical pathway or the alternative pathway. Stabilization of C3bBb is achieved with either P or C3NeF after their binding to C3b and C3bBb, respectively. Control of this amplifying step occurs at three levels: intrinsic decay of the inherently labile C3bBb complex, extrinsic decay-dissociation of Bb from the complex by beta1H, and inactivation of C3b by C3bINA. In the presence of stabilizing factors the control proteins must function in sequence, since C3bINA cannot act on C3bBb; beta1H-mediated decay of protective Bb must precede C3b inactivation by C3bINA. C3NeF, which is found in the sera of some patients with MPGN and persistent depressions of serum C3, circumvents all three controls because of its capacity to create a stabilized convertase that is relatively resistant to decay-dissociation by beta1H. The effector complement sequence is activated by cleavage of C3 and C5, which releases vasoactive and chemotactic peptides, C3a and C5a, and generates the major fragments C3b and C5b. C3b, in addition to its function in the amplifying reaction and the C5 convertases, mediates immune adherence to cells possessing membrane-associated receptors for C3b; this in turn promotes the phagocytic and secretory functions unique to each cell type. Cell-bound C5b serves to assemble the cytolytic complex C5b6789, while fluid-phase C5d generates the hemolytically inactive chemotactic complex C567d...     

Overexpression of complement inhibitor Crry does not prevent cryoglobulin-associated membranoproliferative glomerulonephritis

BACKGROUND: Mice overexpressing thymic stromal lymphopoietin (TSLP) develop mixed cryoglobulinemia with renal disease closely resembling human cryoglobulin-associated membranoproliferative glomerulonephritis (MPGN), including glomerular deposits of immunoglobulins and complement. We assessed the effect of complement inhibition through overexpression of Crry (complement receptor-1 related gene/protein Y), which blocks the classic and alternative pathway of complement activation through inhibition of the C3 convertase, in cryoglobulinemia-associated immune complex glomerulonephritis. METHODS: TSLP transgenic mice were crossbred with animals overexpressing Crry. Mice were sacrificed after 50 days (females) or 120 days (males), and kidneys, blood, and urine were collected from seven mice of each experimental group (wild type, Crry transgenic, TSLP transgenic, and Crry/TSLP doubly transgenic). RESULTS: TSLP/Crry doubly transgenic animals demonstrated expected serum levels of Crry. Renal involvement, both in TSLP transgenic and TSLP/Crry doubly transgenic animals, was characterized by glomerular matrix expansion, macrophage influx, activation of mesangial cells, and deposition of immunoglobulins and complement. Overexpression of Crry did not result in significant improvement of renal pathology or laboratory findings. Expression of recombinant soluble Crry was confirmed by enzyme-linked immunosorbent assay (ELISA) in Crry transgenic animals. However, formation of the membrane attack complex C5b-9 as a marker of terminal active complement components and represented by glomerular C9 staining could not be inhibited in Crry transgenic TSLP mice. CONCLUSION: These results indicate that overexpression of Crry was not sufficient to prevent renal injury in TSLP transgenic mice. We suggest that the inhibitory capacity of Crry may be overwhelmed by chronic complement activation. Further studies need to address the role of complement in cryoglobulinemic glomerulonephritis before therapeutic complement inhibition can be attempted.     

Familial membranoproliferative glomerulonephritis

Four and two male sibs of two separate families who had biopsy-provenmembranoproliferative glomerulonephritis (MPGN) are presented.In the first family four sibs of the first-degree consanguineousmarriage showed the clinical picture of nephrotic syndrome withouthypocomplementaemia at initial laboratory findings. In the secondfamily two affected sibs showed nephrotic and nephritic syndromeson admission. Family investigations showed normal serum complement,immunoglobulins, T-cell subsets, urine analysis, and serum biochemistry.HLA typing in the two families revealed a common antigen HLAA2 in all affected sibs. Some other reports give suggestiveevidence of MPGN in siblings but this is the first report thatshowed the occurrence of MPGN in four sibs. Our data strengthenedthe concept that genetic factors are involved in the developmentof MPGN but additional immunogenetic studies will shed lighton the genetic aspects of the disease.     

Malignancy-associated membranoproliferative glomerulonephritis

An 11-year-old girl with an abdominal desmoplastic round cell tumor, treated with chemotherapy, presented with gross hematuria and proteinuria. Renal biopsy revealed type I membranoproliferative glomerulonephritis (MPGN). The association of a malignant tumor and MPGN is extremely unusual in children, and the pathogenesis of the renal lesion under these circumstances is unknown. Received June 23, 1994; accepted in revised form July 10, 1996; accepted July 11, 1996     

Idiopathic membranoproliferative glomerulonephritis in childhood

Membranoproliferative glomerulonephritis (MPGN), recognized since 1965, is now known to have three forms, designated types I, II, and III. The types are similar in the frequency of hypocomplementemia and clinical course but are dissimilar in glomerular ultrastructure, pathogenesis, mechanisms of complement activation, predisposition to recur in the renal transplant, and, to some extent, in clinical presentation. Although glomerular proliferation is usually diffuse, it may be focal and segmental particularly in mild cases of MPGN I. Hypocomplementemia, present in about 80% of patients, is the result of hypercatabolism of C3 by three mechanisms as well as of diminished C3 synthesis. The hypocomplementemia is unrelated to clinical course or prognosis. Although MPGN I and III both have a high frequency of an extended haplotype on chromosome 6, which has known associations with autoimmune phenomena, and both have a high frequency of inherited complement defects, they are nevertheless dissimilar in glomerular ultrastructure, complement profile, and immunohistology in ways which suggest a wide difference in pathogenesis. Abnormalities in humoral immunity appear not to be involved in MPGN III. Treatment with anticoagulant, antiplatelet and cytotoxic drugs have, in controlled trials, been either ineffective or marginally effective. Long-term use of alternate-day prednisone in high dosage appears to be the most efficacious regimen in both controlled and uncontrolled studies.     

Pathogenic mechanisms in membranoproliferative glomerulonephritis

PURPOSE OF REVIEW: This review considers new information on the pathogenesis of a long recognized and poorly understood form of glomerular injury, membranoproliferative glomerulonephritis. This disease has received growing attention as it is the principal renal manifestation of hepatitis C virus infection, which has become pandemic worldwide. RECENT FINDINGS: This review briefly describes three murine models of membranoproliferative glomerulonephritis suitable for pathogenesis studies. We consider recent evidence implicating innate immune mechanisms in immune and autoimmune-mediated glomerulonephritis, and recent data pointing to the alternative pathway of complement activation in the amplification of glomerulonephritic injury. SUMMARY: Understanding the contribution of complement activation and innate immunity to the evolution of membranoproliferative glomerulonephritis promises to provide new therapeutic targets for this disease. Inhibitors of the complement cascade are already being tested in clinical trials as therapeutic interventions for some human glomerular diseases. Successful tests of this approach in membranoproliferative glomerulonephritis are still awaited. Our understanding of how the innate immune system modulates glomerulonephritis is still in an early stage, and future studies should be directed at identifying targets and specific interventions that may also benefit patients with this disease.     

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.     

Focal segmental membranoproliferative glomerulonephritis in children

Eight patients with focal segmental membranoproliferative glomerulonephritis (FSMPGN) were followed for 5–16 years. Their urinary abnormalities were detected by school urinary screening in seven, and one patient presented with nephrotic syndrome. All but one patient were treated with alternate-day (ALD) prednisolone. With time, urinalysis became normal in six and two continued to have proteinuria with or without hematuria. Serum albumin, cholesterol, and creatinine levels were normal at the last follow-up. Serum C3 returned to normal levels in six, but remained persistently decreased in two. Mesangial proliferation and matrix changes in glomeruli without MPGN lesions were mild. Subendothelial and mesangial electron-dense deposits and deposits containing C3 along capillary walls and mesangium were observed. MPGN lesions and mesangial proliferation improved. No severe growth retardation was observed, but the duration and dosage of ALD prednisolone could be reduced further, since the patients with FSMPGN seemed to have an excellent prognosis.     

Circulating immune complexes in membranoproliferative glomerulonephritis

Circulating immune complexes (CIC), measured by the solid-phase Clq method, were found to be in abnormal concentration in about half of 39 patients with membranoproliferative glomerulonephritis (MPGN). In contrast, they were present, usually in higher concentration, in nearly all patients with active lupus nephritis. Correlations between clinical course and CIC levels in patients with MPGN showed that complexes were always present when the disease was mild or "silent," but when renal impairment developed or was incipient, complexes were nearly always absent. In patients with disease of intermediate severity, characterized by definite proteinuria but without renal impairment, 50% had complexes. The presence of complexes when glomerular abnormality is relatively slight could be interpreted as indicating that the complexes measured were not nephritogenic, or that they program subsequent events that augment glomerular injury in the absence of complexes. The measurement of CIC in MPGN appears to have minimal value both in diagnosis and in determining prognosis.     

Idiopathic membranoproliferative glomerulonephritis in Japanese children

The course of idiopathic membranoproliferative glomerulonephritis (MPGN) in 41 Japanese children (21 boys, 20 girls) is reported. The mean follow-up period was 8 years, 9 months; 29 children with MPGN (71%) were identified by school urinary screening; 32 patients had type I MPGN, 2 type II and 7 type III; 10 patients were treated with multiple low-dose cocktail therapy (MLD), 8 with MLD followed by high-dose alternate-day (ALD) prednisolone and 21 with high-dose ALD prednisolone alone. In 1 patient, MPGN progressed to end-stage renal failure. The serum creatinine level in all of the remaining 40 patients was ≤ 1.3 mg/dl at the last follow-up. Urinalysis was normal in 24 (59%). Of the 17 patients who still had urinary abnormalities, 4 had nephrotic syndrome. The incidence of remission of urinary abnormalities was highest in the patients treated with high-dose ALD prednisolone. Rebiopsy was performed in 33 patients, and revealed slight histological improvement in 11 (33%) patients, moderate improvement in 8 (24%), marked improvement in 5 (15%) and deterioration or no improvement in 9 patients (27%). Relatively few side effects of treatment were observed. The superior outcome of the MPGN patients in this compared with other studies may be the result of earlier detection and treatment.     

A patient with membranoproliferative glomerulonephritis diagnosed by the third biopsy via endocapillary proliferative glomerulonephritis and focal membranoproliferative glomerulonephritis

We present a girl with type I membranoproliferative glomerulonephritis (MPGN) diagnosed by the third renal biopsy. The first renal biopsy was performed at age 11.2 years after microscopic hematuria (which was revealed by school urinary screening) had persisted for 3 months, along with a low level of serum C₃. Pathological examination of the biopsied specimen revealed endocapillary proliferative glomerulonephritis with multiple humps. The serum C₃ level increased to within the normal range 2 months after the first renal biopsy, and the microscopic hematuria disappeared at age 12.3. However, microscopic hematuria, proteinuria, and the low serum complement level reappeared at age 12.8. Pathological examination of a further renal biopsy that was performed at age 13.2 revealed focal MPGN with humps. Prednisolone therapy was subsequently initiated. Fluvastatin was added to her treatment regime when she developed hypercholesterolemia at age 13.6 and was continued even after normal cholesterol levels were reestablished. Pathological examination of the third renal biopsy, which was performed at age 15.2, revealed type I MPGN with humps. Serum C₃ normalized 6 months after the cessation of prednisolone at age 15.9. It is clinically important that patients with nontypical acute glomerulonephritis should be observed over a long period and repeated renal biopsies should be performed.     

Patterns of complement activation in idiopathic membranoproliferative glomerulonephritis, types I, II, and III

Complement profiles on 22 hypocomplementemic patients with membranoproliferative glomerulonephritis (MPGN) type I, on 11 with MPGN II, and on 16 with MPGN III, gave evidence that the nephritic factor of the amplification loop (NFa) is responsible for the hypocomplementemia in MPGN II and the nephritic factor of the terminal pathway (NFt) for the hypocomplementemia in MPGN III. In contrast, in MPGN I, there was evidence for three complement-activating modalities, NFa, NFt, and immune complexes. As a result, four different patterns of complement activation were seen. NFa, found in MPGN II, produces a complement profile characterized mainly by C3 depression. In addition, four of seven (57%) severely hypocomplementemic MPGN II patients (C3 less than 30 mg/dL) had slightly depressed levels of factor B, and one of seven (14%) of properdin, but in all the C5 concentration was normal. In contrast, all eight severely hypocomplementemic patients with MPGN II had depressed C5 and properdin levels, and six of eight (75%) depressed levels of C6, C7, and/or C9. Of eight MPGN III patients with moderate hypocomplementemia, 50% had depressed C5 and properdin levels and the remainder, depressed C3 only. This spectrum of profiles is most likely produced by varying concentrations of NFt. In MPGN I, nine of 23 (39%) had a profile indicating only classical pathway activation; seven of 23 (39%), a pattern compatible with NFt alone; four of 23 (9%), evidence for both classical pathway activation and NFt; and three of 23 (13%), a pattern compatible with NFa. The unique multifactorial origin of the hypocomplementemia in MPGN I, often giving evidence of classical pathway activation, together with previously reported differences in glomerular morphology and clinical features at onset, makes it distinct from MPGN III. Depressed C8 levels were found to some extent in all hypocomplementemic states. The levels were uncommonly depressed in patients with NFa, most markedly depressed with NFt, and moderately reduced with classical pathway activation. The cause is not known. Diagnostically, profiles showing classical pathway activation and low levels of C6, C7, and/or C9 are specific for MPGN I. Those showing only classical activation are likewise diagnostic of MPGN I if systemic lupus erythematosus (SLE) and chronic bacteremia are ruled out.     

Decreasing hypocomplementemia and membranoproliferative glomerulonephritis in Japan

The number of patients with membranoproliferative glomerulonephritis(MPGN) diagnosed in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs in Japan were investigated retrospectively. Fifty-seven children were diagnosed as having MPGN between 1974 and 1997. Of these, 13 patients were diagnosed during period 1 (1974–1979) and 25 during period 2 (1980– 1985). A decreasing trend was observed during periods 3 (1986–1991) (12 patients) and 4 (1992–1997) (7 patients) compared with period 2 (P<0.05 and P<0.01, respectively). A significant difference was also noted when MPGN was compared between periods 1 and 2 (1974– 1985) and periods 3 and 4 (1986–1997) (P<0.01). Serum C3 was measured in 1,282 school children with abnormal urinary findings between 1980 and 1997. Thirty children had hypocomplementemia. The incidence of hypocomplementemia was significantly lower in period 3 (1986–1991) (9 children) and period 4 (1992–1997) (2 children) compared with period 2 (1980–1985) (19 children) (P<0.05 and P<0.01, respectively). New cases of MPGN in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs are decreasing in Japan. The reason for this trend is unknown. Received: 10 August 1999 / Revised: 22 November 1999 / Accepted: 23 November 1999     

Focal and diffuse membranoproliferative glomerulonephritis in children

Characteristic deposition of C3 has been reported in type I membranoproliferative glomerulonephritis (MPGN). Immunofluorescence microscopy shows diffuse granular deposition of C3 along the majority of capillary loops with lobular pattern. To determine the specificity of this immunofluorescence finding which might aid in distinction between type 1 MPGN, particularly focal MPGN, and the other glomerulopathies, 530 renal biopsies from 437 children were studied retrospectively. Nineteen patients showed diffuse granular deposits of C3 along the capillary walls with lobular distribution. Three patients had lupus nephritis. Nine patients showed the light microscopic changes of diffuse type I MPGN with the characteristic double-walled capillaries. Six patients showed the changes of focal MPGN, and 1 had diffuse mesangial proliferation but without double contours, and they were regarded as examples of a mild or early form of MPGN. A similar deposition of C3 was not seen in the 418 patients with other conditions. We concluded that diffuse granular deposits of C3 along the capillary walls with a lobular distribution appear to be confined to type I MPGN and lupus nephritis and are seen in all patients with diffuse and focal type I MPGN.     

Clinicopathologic study of adult-onset membranoproliferative glomerulonephritis

We analyzed clinicopathologic characteristics of adult-onset membranoproliferative glomerulonephritis (MPGN) by comparing two tentatively-classified subgroups. Group A consisted of 9 patients in whom more than 50% of glomeruli showed mixed segmental and global duplication of glomerular basement membrane (GBM), and Group B 9 patients with global duplication of GBM. Group A showed a tendency for more favorable clinical course and outcome than Group B. Nephrotic syndrome was present in 33% of Group A and 100% in Group B, hypertension in 22% and 44%, hypocomplementemia in 44% and 67% at the time of renal biopsy. Deterioration of renal function, at comparable durations of follow-up of 62 +/- 12 (M +/- SE) and 53 +/- 13 months, was observed in 22% of Group A and 56% in Group B, respectively. Histologically, mesangial proliferation and tubulointerstitial change were more pronounced and frequency of sclerosing glomeruli was greater in Group B. There was also a negative correlation between the extent of global double contour and renal function as assessed by creatinine clearance at the time of renal biopsy (r = -0.55, P less than 0.05). These results indicate that the high incidence of global double contour, in addition to the presence of marked tubulointerstitial change and sclerosing glomeruli, may relate to progressive deterioration of renal function in MPGN. That outcomes for Group A and Group B may be different when clinical parameters, including the durations from onset of symptoms to the time of biopsy and length of follow-up periods, are comparable also indicates that these two groups should be considered separate entities, at least on the basis of clinical results.