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.