Kupffer cells are fixed macrophages found in the walls of hepatic sinusoids. Like other members of the mononuclear phagocytotic system, they are derived from monocytes.
This animal was injected with tyrpan blue. For most cells, trypan blue is a vital dye. It is excluded from living cells and enters into and stains dead cells. However, trypan blue is also taken up by living cells actively engaged in phagocytosis.
In this liver, trypan blue demonstrates the presence of phagocytosis in Kupffer cells. These macrophages readily phagocytize and retain the foreign molecule, trypan blue.