Induction of in situ immune complexes in rat glomeruli using avidin, a native cation macromolecule.

This reports a perfusion study using avidin, a native cation macromolecule, followed by rat anti-avidin antibody given directly into the rat renal artery. After 10 min perfusion with avidin, an indirect immunofluorescent study revealed a fine granular distribution of rat IgG along the glomerular capillary loops; an electromicroscopic study showed small particles at sites identical to the position of the anionic sites of the glomerular basement membrane (GBM). After 10 min perfusion with anti-avidin antibody following avidin, rat IgG was heavily deposited along the glomerular capillary loops and electron-dense deposits were observed subendothelially. Rats were administered also intravenous avidin followed 1 h later by rat anti-avidin antibody. The staining pattern of rat IgG, initially almost linear, became granular along the glomerular capillary loops by 72 h. Twenty-four hours later small electron dense deposits, initially localized subendothelially, were found in the subepithelial region with swelling of epithelial foot processes. These observations show that avidin binds to the anionic sites of the GBM, acts as a planted antigen, and results in in situ immune-complex formation.