Evidence of a role for local complement expression in a murine model of progressive glomerulonephritis.

C57/B6 mice received intraperitoneal horse spleen apoferritin (4 mg) with lipopolysaccharide (0.05 mg); control mice received 0.15 M NaCl. Control and treated animals were killed weekly for 6 wk; blood and urine specimens were obtained, and tissue samples were secured. Treated animals showed evidence of significant chronic disease, with proteinuria, hematuria, and uremia. A mild glomerulonephritis was present at 2 wk, with significant proliferative glomerulonephritis at 4 wk, progressing to chronic disease with tubulointerstitial changes at 6 wk. Changes at each time period were uniform between animals. C3 mRNA was first detected by in situ hybridization at 3 wk. Message was restricted to proximal tubular and periglomerular epithelial cells. Presence of C3 message preceded the development of interstitial inflammation and fibrosis by 1-2 wk, and its location and intensity paralleled the evolving interstitial disease. Although extensive mesangial C3 protein deposits appeared early, there was never C3 message in glomeruli or infiltrating cells. Before C3 message became apparent, two cytokines known to up-regulate C3 transcription in vitro, IL-1 and IL-6, were detected by immunohistochemistry. The temporal sequence in this model is consistent with our hypothesis that local synthesis and activation of C3 in tubular epithelium is important to the interstitial component of chronic glomerulonephritis. The process is independent of the deposition of circulating complement in the glomerulus, but may be triggered by glomerular cytokines.