Tissue and glomerular deposition of globulin aggregates

We studied the behavior of AgGG, a model of iCs, in the rat. The clearance of radiolabeled AgGG from the circulation was found to follow first-order kinetics. The t1/2 of the AgGG increased markedly with increases in dose administered, whereas the absolute rate of removal appeared to approach a maximum. The bulk of the AgGG cleared was found in the liver, and less than 1% was found in spleen, lung, or kidney. All these features are typical of the behavior of macromolecules removed from the circulation by the RES. Specific glomerular deposition was studied at various dosages by isolating glomeruli and measuring the fraction of injected aggregate that was trapped. This fraction represented less than 10% of total renal deposits. Moreover, when animals were sacrificed at an interval of 1 t1/2 after the injection of the corresponding dose, the fraction deposited in glomeruli remained constant. The significance of this finding is discussed in relation to the pathogenesis of glomerulonephritis.