The influence of phagocyte function on glomerular localization of aggregated IgM in rats.

The blood clearance and hepatic localization of aggregated human IgM (AIgM) were studied in relation to the glomerular localization patterns in rats. AIgM was cleared rapidly from the circulation by sinusoidal cells in the liver, monomeric IgM (MIgM) was cleared less rapidly. Localization of AIgM within the glomerulus was dependent on the level in the blood. Low doses led only to a mesangial localization, whereas high doeses resulted in a localization along the capillary walls. Immunoelectron microscopy showed that in the glomerular capillaries the AIgM was localized within endothelial cells or subendothelially, and did not occur within the glomerular basement membrane. Inhibition of the hepatic uptake of AIgM by colloidal carbon resulted in increased levels of circulating AIgM and prolonged the deposition of AIgM in the glomerular capillaries.