Removal of subepithelial immune complexes with excess unaltered or cationic antigen

Since cationic molecules are known to pass through the lamina densa of the glomerular basement membrane at higher rates than anionic molecules, the ability of cationic antigen to disperse subepithelial glomerular immune deposits was investigated in rats. Subepithelial glomerular immune deposits were formed in rats by the sequential administration of cationized human serum albumin (HSAED) and purified rabbit antibodies to human serum albumin (HSA). In vitro the addition of fifty-fold excess HSA or HSAED to immune precipitates formed with HSAED and antibodies to human serum albumin (antiHSA) solubilized the precipitates to comparable degree. Excess HSA or HSAED was given intravenously to rats which already had HSAED-antiHSA immune deposits in glomeruli. Serial renal biopsies were obtained and examined. Control animals received saline or nonspecific cationic molecules, protamine sulfate or cationized rabbit serum albumin, without any effect on the persistence of immune deposits in glomeruli. The injection of 10 mg of HSAED caused complete disappearance of glomerular immune deposits by 48 hours. In contrast, 100 mg of HSA was required to achieve the same effect. Thus, cationic antigens are more efficient than anionic antigens in the removal of subepithelial glomerular immune deposits.