An ultrastructural study of peritoneal mononuclear phagocytes from iota carrageenan injected mice.

Mononuclear phagocytes harvested from peritoneal cavities of mice injected intraperitoneally 24 h previously with iota carrageenan were invariably vacuolated or lysed. The incidence of lysed cells was approximately 25%. Carrageenan could be identified as fibrillar material within phagolysosomes of varying size, and retention of the fibrillar structure of this material, even within lysed cells, suggests that iota carrageenan is relatively resistant to biochemical degradation and hence persists within the phagolysosomes. The limiting membranes of many of the larger vacuoles were frequently ruptured, probably indicating osmotic stress on these membranes as the phagolysosomes swell.