Evaluation of Indium-111-Polyclonal Immunoglobulin G to Quantitate Atherosclerosis

results in a grossly modified lipoprotein that rapidly accumu lates withinmacrophages(6). Oxidationof LDL can be pre vented by suitable antioxidants,which appear effective in reducing atherosclerosis progression in Watanabe heritable hyperlipidemic (WHHL) rabbits (7). Another intervention for preventingoxidative modificationof LDL is treatment with ethinylestradiol(8), which also decreases serum lipids (9).OxidizedLDL ishighlyimmunogenic.In WHHL rabbits and in cholesterol-fedNew ZealandWhite (NZW) rabbits, increased concentrations of circulating autoantibodies were found (10). Interventionmay decrease concentrationof cir culating LDL-antibody complexes and the amount of im mime complexes incorporatedinto atheroscleroticlesions. The clinical use of drugs designed to lower serum cho lesterol and prevent LDL oxidation has increased the need for early lesion detection and therapy monitoring. Indium 111-labeledpolyclonal immunoglobulinG (IgG) scintigra phy has been used successfully in the detection of early atherosclerosis induced in rabbits by endotheialization of the aortawith a balloon catheter (11)andin humansat sites of severe arterial narrowings (12). The rationale for this technique is based on the fact that macrophagestrappedin the subendotheial space express large numbers of Fc re ceptors that can be imaged with molecules that bind to these receptors (11). On the other hand, circulating im mime complexes can compete with this radiolabeled II gand. In this report, we describe efforts to optimize scin tigraphic detection of atherosclerosis with “In-IgG. Noninvasive scintigraphicresults were compared with cx vivo analyses of incorporated radioactivity as well as with histological staining.