Phagocytosis of protamine-heparin aggregates by mouse peritoneal exudate cells.

Protamine--heparin aggregates (PHAg's) were injected intraperitoneally into thioglycollate-prestimulated mice, peritoneal exudate cells, chiefly macrophages (M phi's) being collected after 2, 15 and 60 min, 6 h, and 30 h for electron microscopy and histochemistry. An intensive phagocytosis of PHAg's was seen even after 5 min and extracellular spaces were cleared of them after 60 min. The less rapid intracellular digestion and breakdown of PHAg's were accompanied by a gradual disappearance of their outer mucopolysaccharide layer. In vitro phagocytosis (60 min in MEM) proceeded in a similar way but more slowly. Coating of PHAg's with immunoglobulin was documented in vitro by ultrastructural enzyme immunocytochemistry. Thus the exudate M phi's are capable of rapid and efficient ingestion of PHAg's which is probably supported in vivo by the interaction of PHAg surface with some exudate components. On the other hand, the intracellular digestion of PHAg's, especially of their mucopolysaccharide shell, is far more protracted.