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Recent reports suggested that the presence of terminal complement complex (C5b-9) in urine from patients with idiopathic membranous nephropathy (IMN) may indicate on-going immunological damage. This report documents the relationship between C5b-9 excretion and clinical outcome in 35 adult patients with biopsy-proven IMN and progressively declining renal function. There were two groups of patients. Group I received one of three treatment regimens: prednisolone alone, prednisolone and chlorambucil, or prednisolone and cyclophosphamide (N = 22). Group II received no immunosuppressive therapy (N = 17). Three of the 18 patients receiving immunosuppressive drugs had more than one treatment regimen as they experienced a clinical relapse during the study period; hence 22 treatments were available for analysis. Urine samples were collected regularly and urinary C5b-9 (uC5b-9) was determined by ELISA. Both groups were similar with respect to age, sex distribution, and the duration of follow-up. An improvement in proteinuria and creatinine clearance was noted in the immunosuppressed group. Thirty-five patients were excreting C5b-9 initially (18 from group I and 17 from group II); 17 patients continued to excrete C5b-9 at the end of the observation period. These 17 patients had a significantly worse clinical outcome when compared to the 18 patients whose C5b-9 excretion became negative, either spontaneously or with treatment (P < 0.005). These results indicate that continuing C5b-9 excretion is correlated with a poor clinical outcome. They also suggest that uC5b-9 is a dynamic marker of ongoing immunological injury, and therefore may be useful in the initial assessment and monitoring of patients with IMN and in identifying patients who may derive benefit from immunosuppressive therapy.

We have previously reported that urinary excretion of the complement activation products C3dg and C5b-9 in human membranous nephropathy (MN) correlated with clinical outcome in a cross-sectional analysis. We report here the results of a retrospective longitudinal study of the temporal relationship between urinary C3dg and C5b-9 excretion and clinical parameters. A group of 23 adult patients with biopsy-proven MN were studied over a mean time period per patient of 3.5 years. Freshly voided urine samples were collected regularly; C3dg and C5b-9 were measured by ELISA (mean number of samples per patient = 13). During the period of the study, nine patients with declining renal function (group A) were treated with a standard steroid regimen. Serum creatinine had improved or stabilized in seven of these patients at the end of treatment. All nine patients were excreting C3dg and C5b-9 before treatment. Six other patients with declining renal function (group B) were not treated with steroids because of clinical contraindications. Serum creatinine continued to increase during the study in four of these six patients. C3dg and C5b-9 were present in the urine samples of these six patients on the majority of dates tested. Eight patients maintained stable renal function during the study (group C), either normal (6 patients) or impaired (2 patients). Of these patients, six were consistently negative for urinary C3dg and C5b-9 despite persistent proteinuria, and one patient who was initially positive became negative within 15 months, and remained negative for the rest of the study period. One patient was positive on one of 12 occasions tested. These results suggest that urinary complement activation products indicate ongoing active glomerular damage and may prove to be important determinants for the introduction and monitoring of therapy.

We have measured complement activation markers, C3dg and C5b-9 in plasma and urine from patients with idiopathic membranous nephropathy and IgA nephropathy. There was no significant difference in levels of plasma C5b-9 between the patient groups. However, high plasma concentrations of C3dg were associated significantly with IgA nephropathy with 45% of patients having levels over 25 U/ml (P less than 0.001). High concentrations of urinary C3dg and C5b-9 were associated significantly with membranous nephropathy (43% and 43% of the patient group, respectively) compared to patients with IgA nephropathy (10% and 0%, respectively, P less than 0.001). In a retrospective analysis of 31 patients with membranous nephropathy, 66% of patients with high initial urinary C5b-9 showed an unstable clinical course compared to 18% of patients with initially absent or low C5b-9 (P less than 0.001). We suggest that high urinary C5b-9 identifies those patients with a membranous lesion which retains an active immunological component contributing to the pathology of progressive glomerular damage.

Patients with heavy proteinuria have an increased incidence of venous thrombosis and coronary heart disease (CHD). They also exhibit perturbations in lipoprotein metabolism. Lipoprotein (a) (Lp(a)) predisposes to CHD; it may also promote intravascular thrombosis since it contains apolipoprotein (a), which could act as a competitive inhibitor of plasminogen activation. We have measured the concentration of serum Lp(a) in 10 men with proteinuria due to idiopathic membranous nephropathy (IMN), in eight men with a similar diagnosis but who were in remission, and in 103 healthy men. Serum Lp(a) levels were significantly elevated in the men with active IMN, having a median value of 31.3 (range 3.2-75.0) mg/dl, whereas they were 8.4 (3.4-31.5) mg/dl in the patients in remission, which was similar to the value of 11.3 (< 0.8-87.4) mg/dl found in the healthy controls. Lp(a) is unique in containing an apolipoprotein which is a giant mutant of plasminogen and it is thus possible that the high circulating levels of Lp(a) contribute to the vascular morbidity associated with proteinuria by promoting thrombosis or atherogenesis or both.