The specificity of uptake of model immune complexes and other protein aggregates by the murine reticuloendothelial system

We have studied the selectivity of the murine reticuloendothelial system in recognizing and removing from the blood model immune complexes and several aggregated proteins. Although both IgG anti-DNP model immune complexes and micro-aggregated albumin exhibited rapid hepatic uptake, which is saturable, they did not cross-inhibit each other. Aggregates of ovalbumin, a glycoprotein rich in mannose (a sugar recognized by Kupffer cells), had no effect on the uptake by the liver of either IgG immune complexes or micro-aggregated albumin. The finding that transferrin aggregates were not taken up by the liver at all suggests that aggregation alone is not sufficient to overcome the lack of a specific hepatic receptor for that protein. Thus, several mechanisms exist whereby aggregated proteins can be cleared from the blood by the reticuloendothelial system, an observation consistent with the selective failure of reticuloendothelial function found in several human diseases.