[Changes of complement in immune complex glomerulonephritis induced by cationized antigen].

Abstract

Complement system takes an important role in the pathogenesis of immune complex glomerulonephritis. In this study the precise changes of serum complement and its deposition in the glomeruli were investigated in the mice models induced with cationized bovine gamma-globulin (CBGG). Balb/c mice preimmunized with CBGG were injected intravenously with CBGG three times every 24 hours. Proteinuria and hypoalbuminemia have developed from day 3 until the death on day 9-13 of progressed azotemia. This nephritis resembled to mesangial proliferative glomerulonephritis histopathologically. Immunofluorescent study revealed granular deposits of CBGG, IgG, A, M and C3 along the glomerular capillary loop. Serum C3 decreased to about 50% of normal controls within 1 hour after challenge of antigen and plasma C3 conversion evaluated by crossed-immunoelectrophoresis, occurred in accordance with C3 reduction and then decreased. Immunofluorescent study showed a big difference in the mode of deposition among IgG, CBGG and C3. The most intense deposits of C3 in the glomeruli were seen 12 hours after challenge of CBGG, and then gradually decreased until the next challenge. IgG and CBGG antigen deposited most intensely soon after the challenge of antigen, and gradually decreased. These results led us to conclude that there existed two phases of complement activation in this immune complex induced mice glomerulonephritis; an early phase activation of complement by antigen-antibody complexes in the circulation and later phase activation of complement by immune complexes after deposition of them in situ glomeruli.