Reticulo-endothelial system RES

The use of the reticulo-endothelial system (RES) was the first approach to liver contrast agents. As an adjunct, spleen imaging would also be possible with a contrast agent that is taken up by the RES. The Kupffer cells of the liver, which represent 10% of all hepatic cells, constitute the major portion (80-90%) of all fixed macrophages and they are extremely effective in the phagocytosis of all types of particles. The downside of the use of this mechanism, however, is the concomitant release of toxic mediators that might and - as a matter of fact - often has made this approach non-feasible. Adverse events provoked by the mediators are changes in blood pressure (most often hypotension) and fever. 

Depending on their size and surface charge, parenter-ally administered liposomes interact with the reticulo endothelial system (RES) and provoke an immunological response. After being marked by the adsorption of certain serum proteins, called opsonins, they are identified as an invader and destroyed by specific immune cells mainly in the liver, spleen, and bone marrow. 

The uptake of MoAb-based delivery systems by the reticulo-endothelial system (RES) is another drawback to these systems. It has been suggested that only 0.1-1% of the administered dose of antibody-based systems reaches non-RES sites, with 8 /o dose reaching... 

The body recognizes hydrophobic particles as foreign. The reticulo-endothelial system (RES) eliminates these from the blood stream and takes them up in the liver or the spleen. This process is one of the most important biological barriers to particles-based controlled drug delivery [15]. 

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