Abstract 658: Macrophage Dynamics in Inflammation: Tree Ring--Like Growth of Macrophages in Layers Within Atherosclerotic Plaques

The mechanisms that control macrophage accumulation and retraction from plaques are fervently debated. We had earlier wondered if monocyte-derived cells might be driven to become motile cells resembling dendritic cells, capable of leaving plaque, under conditions when macrophage content in plaques waned. Thus, our laboratory developed a technique that allows the use of fluorescent phagocytic tracers to quantitatively monitor macrophage influx into plaques as well as the potential emigration of macrophages out of plaques. The phagocytic tracer was not removed from plaques when plaque macrophage content receded in conjunction with a stark lowering of plasma cholesterol, arguing that macrophage loss does not result from robust emigration of macrophages out of plaques. Nonetheless, here we show that the distribution of the phagocytic tracer was very different under conditions when macrophage content wanes, as the tracer is distributed near the arterial lumen in this case, versus conditions when macrophages in...