SllmnlaryImmunopathological evidence suggests that activation of the alternative pathway of complement (AP) is involved in membranoproliferative glomerulonephritis (MPGN) and in immunoglobulin A nephropathy. In this report we describe an AP dysfunction-associated factor that was isolated from the serum and urine of a patient with hypocomplementemic MPGN. Extensive glomerular deposits of C3, properdin, and of the terminal complement components were observed in the kidney of the patient. In her serum the AP hemolytic activity was virtually absent. When mixed with fresh normal serum, the patient's serum induced a 96% C3 conversion during a 30-min incubation at +37~ This activity was found to be due to a circulating factor that by immunochemical characterization proved to be a 46-kD monoclonal immunoglobulin X light (L) chain dimer (~L)-Purified ~,r, but not control ~, or Ic L chains from patients with L chain disease, activated the AP in a dose-and ionic strength-dependent manner. Functionally, XL was differentiated from C3 nephritic factor (an autoantibody against the AP C3 convertase, C3bBb) by its inability to bind to and stabilize the C3bBb enzyme. Instead, Jkr was observed to interact directly with the AP control factor H. Thus, hL represents a novel type of immunoglobulinrelated AP-activating factor with the capacity to initiate alternative complement pathway activation in the fluid phase.

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The median urinary TGF-beta 1 excretion (pg/mg creatinine) was significantly higher (1730; range 60-16,970) in MGN patients than in the healthy controls (300; 30-1330; P < 0.0001). In renal allograft recipients the excretion was 840 (250-3440; P < 0.0001 vs healthy controls), in IgA GN it was 1130 (30-4910; P = 0.039), and in proteinuric patients it was 39 (29-165; P = NS). In MGN but not in the proteinuric controls or renal allograft recipients, urinary TGF-beta 1 correlated with urinary albumin excretion (r = 0.86, P < 0.0001) but no correlation with renal function or the duration of the disease was found. Urinary TGF-beta 1 at renal biopsy correlated with interstitial cellular inflammation and its excretion 1 year before the biopsy correlated with indices of sclerosis/fibrosis. Immunosuppressive therapy significantly decreased urinary TGF-beta 1 from 2800 (1610-16,960) to 840 (170-1600) pg/mg creatinine (P = 0.028). Patients with persistent nephrotic syndrome and/or declining renal function had a higher initial TGF-beta 1 excretion (median 3680; 1830-7420 pg/mg creatinine) than those entering partial or complete remission (1060; 60-1960; P = 0.003) within 12 months from sampling.

These findings show that the urinary PIIINP-to-creatinine ratio reflects the ongoing fibrotic processes in the kidney. Tubular epithelial cell injury may initiate the fibrotic processes, and elevated concentrations of urinary TGF-beta 1 and alpha(1)M may associate with the increased production and deposition of collagen type III in the graft. We conclude that measurements of urinary excretion of PIIINP can be used as an early noninvasive indicator of renal fibrosis after kidney transplantation.

We show proximal tubular injury, measured by increased urinary alpha1M, to be present even in normoalbuminuric patients and to be associated with increased excretion of TGF-beta1 and with the annual deterioration of glomerular filtration rate. These findings show increased alpha1M/creatinine ratio to be an early and sensitive indicator of poor long-term outcome in renal-transplant patients.