Macrophages are versatile; not only do they help clean up our blood by gobbling up old and dying cells/tissue, but they also have an appetite for things that aren't supposed to BE in our body. Furthermore, they have the ability to take a "piece" of that foreign material, much like an Antigen Presenting Cell (APC), and display it on its surface so that our immune system "marks" it as being bad and knows to react against it in future encounters!
Our pic just shows a collage of macrophages in illustration form and its corresponding "real image" counterpart. Can anyone explain the significance of the macrophage foam cell? The "foam" in the cell is actually lipid, therefore, if a macrophage has been gobbling up lipids, it is an indication of high levels of lipids within the bloodstream. This means that atherosclerosis is likely present. Also, foam cells can indicate certain types of bacterial infections.