Induction of macrophage colony forming cells in the pleural cavity

A class of colony forming cells was induced in the pleural cavity of mice after a local injection of thioglycollate medium (TM). They formed colonies in both soft agar and liquid medium cultures. Only mononuclear phagocytes were observed in these colonies. The plating efficiency was 2.2% (1.3 to 3.9%) in AKR mice 3 days after intrapleural injection of 0.5 ml TM. A small but significant increase in pleural effusion colony forming cells (PL-CFC) was also observed in mice receiving TM i.p. but none in those receiving TM by s.c. injection. Pleural effusion CFC appeared to be adherent cells and resembled mouse peritoneal exudate colony forming cells in terms of growth requirement, having a long lag period before proliferation and sensitivity to ionizing irradiation.