Electron microscopical study of rat mast cell maturation.

The development of peritoneal mast cells in rats in the early post-natal period was found to take 7-8 weeks. A slightly shorter time was needed for the reappearance of mature peritoneal mast cells following their total destruction in adult rats. In both groups of animals mast cell ultrastructure was studied in successive phases of development. The maturation process was gradual, but no well-defined morphological stages could be demonstrated. The morphology of young peritoneal mast cells seems to indicate that they arise in the peritoneal fluid from macrophage-like cells.