The epithelial cells that line the gut are smooth because the microvilli normally found on them have been blunted (green arrowhead). The area beneath the epithelial cells, the lamina propria, is filled with numerous round cells with a 'foamy' appearance: these are the macrophages (black arrowheads). Extracellular fat has also accumulated in this area (white arrowhead). The tissue is stained with hematoxylin and eosin stain.
IMAGE CREDIT: Micrograph by Nephron (CC BY-SA 3.0).