Reticuloendothelial system and glomerular deposition of heat-aggregated human IgG

The influence of functional impairment of reticuloendothelial system on glomerular deposition of heat aggregated human IgG (HAIgG) was studied. I-125 HAIgG was injected to mice treated either with dextran-containing 0.9% saline or with the saline alone. The HAIgG clearance rate from the blood decreased in the dextran-treated mice. The chronologically measured HAIgG contents in the liver, spleen and glomeruli increased in the dextran-treated animals. Immunofluorescent technique also demonstrated an increase in HAIgG and host C3 in the glomeruli. The glomerular hypercellularity was not demonstrated morphologically. Assuming that the function of the hepatic Kupffer cells principally affect the clearance rate of the foreign macromolecules from the blood, it is likely that the dextran administration impaired the function of these cells to digest the phagocytosed HAIgG, and that consequently the injected HAIgG stayed longer in the blood. Thus, increased supply of the HAIgG from the blood and/or the dextran-induced reduction of digesting function of the mesangial cell per se might have led to the accumulation of glomerular HAIgG. We suggest, therefore, that even small amount of immune complex may induce immune complex-mediated glomerular lesion, when associated with long lasting functional impairment of the Kupffer cells.