Formation of mononuclear phagocyte (macrophage) colonies by mouse spleen cells in liquid culture. I. Kinetics of appearance of colonies and characterization of macrophage colony-forming cells.

Abstract

When spleen cells of the adult mouse were tested for the formation of mononuclear phagocyte (macrophage) colonies by the liquid culture technique with an incubation period of 7--8 days, about 100 macrophage colonies were produced from 1 X 10(6) cells. The number of macrophage colonies appearing after 2 days of incubation was small, but thereafter increased progressively up to at least 8 days. In the later stages of incubation (after day 6) large colonies consisting of more than 100 cells appeared. Macrophage colonies in the early stages consisted almost solely of macrophages. On day 6 significant numbers of small round mononuclear cells with no detectable phagocytic activity were seen in the center of large colonies, and by day 8 marked crowding of these cells had occurred. The peripheral region of the large colonies consisted mainly of macrophages and the intermediate region of middle-sized round or slightly stretched cells with weak phagocytic activity. Approximately two-thirds of the colony-forming cells still remained after glass-adherent cells were removed from the spleen cells by passing over a glass-bead column. In cultures of glass-nonadherent cells macrophage colonies were not generated in the early stage. The number of colony-forming cells did not change significantly even after actively phagocytic cells were rigorously removed from the spleen cells. In addition, no macrophage colonies were generated in cultures of spleen cells treated with mitomycin C.