THE DIFFERENTIATION OF MONONUCLEAR PHAGOCYTES

TLDR

Mouse peritoneal phagocytes stimulated with bacterial lipopolysaccharide undergo similar morphological and biochemical changes. In vitro, unstimulated mouse peritoneal monocytes differentiate into mature macrophages, progressively enlarging, accumulating phase‑dense granules, mitochondria, and lipid droplets, and exhibiting marked increases in acid phosphatase, cathepsin, and β‑glucuronidase activity, reflecting lysosome‑like organelle formation.

Abstract

The in vitro differentiation of homogeneous populations of monocyte-like cells from the unstimulated mouse peritoneal cavity is described. Under the conditions employed, a progressive increase in cell size occurs without significant cell division. This process is characterized morphologically by the accumulation of phase-dense and neutral red-positive granules, mitochondria, and lipid droplets. The phase-dense granules react strongly for acid phosphatase. Biochemical determinations indicate marked increases in the total content and specific activity of acid phosphatase, cathepsin, and ß-glucuronidase. The production of acid phosphatase is more rapid and extensive than that of the other two hydrolases. From these data it appears that the conversion of a monocyte-like cell to a mature macrophage is accompanied by the formation of increased numbers of lysosome-like cytoplasmic organelles. Mouse peritoneal phagocytes stimulated in vivo with a bacterial lipopolysaccharide undergo a similar series of morphological and biochemical events.