Glomerulitis induced by cationized bovine serum albumin in the rat

The effects of injected native and cationized bovine serum albumin (BSA- and BSA+ respectively) were evaluated in rats which subsequently received anti-BSA. Thrombocytopenia, low creatinine clearance (Ccr), increased proteinuria, capillary swelling, mild tuft necrosis and BSA+ deposits in glomeruli resulted within 24 h of BSA+ injection. Later BSA+ produced mesangial expansion glomerular capillary wall (GCW) thickening and deposits of BSA+ accompanied by rabbit anti-BSA and rat anti-BSA which correlated well with small mesangial, subendothelial and subepithelial electron-dense granular accumuli. These latter enlarged considerably after the injection of anti-BSA. BSA- controls showed minimal or no lesions. The disappearance from the blood (t1/2) of a single dose of immune complexes (IC) prepared with chromatography-purified, radioiodinated anti-BSA - BSA- and BSA+ was determined in another group of rats. The t1/2 of BSA- anti-BSA was 42.8 h (95% confidence: 39.8-46.2) while that of BSA+ anti-BSA was 52.5 h (48.1-57.8). These results suggested that serum sickness glomerulitis developed only in rats injected with BSA+, due to in situ IC which presumably grew by accretion of foreign anti-BSA. Circulating IC may have developed and colocated with the latter, with dissociation and recombination at these sites. It is postulated that the functional-immunomorphological changes and the slow removal of cationized IC reported herein could be explained by the highly positive net charge of the injected antigen.