Changes of complement breakdown products and terminal complement complex in patients with acute glomerulonephritis

In this study we examined the role of the complement system in Acute glomerulo nephritis (AGN). Breakdown products of complements (iC3b, C4d and Bb) and Terminal complement complex (TCC, SC5b-9 complex) in plasma samples were measured by ELISA. The microassay plates were coated with monoclonal antibodies which bind specifically to human iC3b, C4d, Bb and SC5b-9 complex. This assay accurately quantitates small amounts of in vivo complement activation. The plasma samples were drawn from patients with AGN and other glomerulonephritis. There were some patients with various glomerulonephritis whose plasma iC3b, C4d and Bb concentrations were higher than those in normal human. However specificity was not found, The ratios iC3b/C3 and C4d/C4 were increased in the early stages of AGN, but plasma Bb concentrations revealed no significant changes. Plasma SC5b-9 complex concentrations were increased in the early stages of AGN. C3c, C3d, C4d and SC5b-9 were found to be localised in the glomeruli of those AGN patients. It is suggestive that in these cases of AGN (especially case 2) complement activation is predominantly mediated through the classical pathway and TCC is formed by this activation. This complement activation in the blood and the renal tissue is presumed to be involved in the initiation and progression of AGN.