Significance of Sudan III staining in macrophages.

Peritoneal macrophages of mice, 48 hr after intraperitoneal administration of albumin (egg white), were studied. Almost all granules in the cytoplasm of macrophages stained by the supravital staining with neutral red were revealed to be colored brick red by the staining with Sudan III in the smear preparation. Because of lack of lipids in the inoculum, it is difficult to explain that these granules stained with Sudan III were lipids phagocytosed. The observation led the suggestion that the Sudan III stained granules in macrophages were out of all relation to lipids phagocytosed and that the granules indicated some functional phage of macrophages.