Endocytosis and formation of macrophage polykarya: an ultrastructural study.

Mononuclear phagocytes in foreign body granulomas become entrapped by the lamellipodia or enter the intracytoplasmic membranous labyrinth of macrophage polykarya. Evidence of membrane fusion was found in such instances and it is suggested that the internalisation of the mononuclear phagocyte is allied to the motility of the syncytium. This concept is also supported by the reports of other authors who emphasise the role of endocytosis in the formation of macrophage polykarya. The net effect of such a mechanism is growth of the syncytium.