Exocytosis by macrophage polykarya: An ultrastructural study

Macrophage polykarya selectively secrete their lysosomal contents directly into the extracellular space or into the intracytoplasmic membranous labyrinth. Fusion of the lysosomal membrane with the plasmalemma or with the cytoplasmic labyrinth results in the release of the lysosomal contents. The labyrinth, however, was shown to be essentially similar to the plasmalemma, hinting that comparable mechanisms are involved in both instances. The process of secretion is unrelated to motility and phagocytosis and may be important in the extracellular degradation of biological material.