Proliferation, kinetics, and fate of monocytes in rat liver during a zymosan-induced inflammation.

The fate and kinetics of monocytes, recruited to the liver by a single zymosan injection, were investigated by light (LM) and electron (EM) microscopy combined with peroxidase cytochemistry and latex phagocytosis. Ultrastructural and cytochemical differences between these cells and resident Kupffer cells persisted during a 7-day period, demonstrating the existence of two types of hepatic mononuclear phagocytes. Both cell types exhibited a pronounced mitotic activity during their numerical increase. Next to peroxidase-positive (POP) Kupffer cells and monocytes, peroxidase-negative (PON) mononuclear phagocytes were observed. These may represent a monocyte subset and/or possibly Kupffer cell precursors.