Possible involvement of terminal complement complex in active Heymann nephritis

We investigated whether the appearance of various complement components in renal deposits of immune complexes correlated with the development of proteinuria in rats with active Heymann nephritis. Sequential kidney biopsy specimens and serum samples were obtained from Lewis rats immunized with Fx1A in complete Freund's adjuvant. Circulating antibodies against purified auto-antigen renal tubular epithelial glycoprotein, as measured by ELISA, were found in the circulation together with a diffuse granular deposition of IgG1, IgG2a, and IgG2b in the glomeruli within 2 weeks after immunization. Biopsy specimens taken 4 weeks after immunization showed diffuse deposition of C4 and C3, which indicated that activation of complement by the classical pathway had occurred. The detection of the C5b-9 complex of complement in glomerular deposits coincided with the development of abnormal proteinuria indicating that the glomerular damage in this autoimmune disease may be caused by complement-mediated lesions in the glomerular capillary walls.