Developmental changes in intestinal globule leukocytes of normal rats.

The changes in the number, distribution, and ultrastructure of globule leukocytes (GL) during postnatal development were investigated in the intestinal epithelium of non-infected healthy rats. Intestinal GL were abundant in normal newborn rats even in the absence of infection. They subsequently decreased markedly to the adult level by the fourth week. Ultrastructurally, morphological variations suggesting maturation of the cells were observed in the GL during development. These changes could be noted neither in the mucosal mast cells (MMC) nor in the granular intra-epithelial lymphocytes. Morphological differences between GL and other cells were evident in adult animals. Most notably, paracrystalline structures were found exclusively in the granules of the GL. Immunohistochemically, both the GL and MMC were stained with anti-serotonin, but not with anti-IgE. Degranulation of GL in developing rats was caused by repeated intraperitoneal administration of dexamethasone. Neither GL nor MMC were affected by compound 48/80. These results indicate that (1) the GL and MMC are derived from a common ancestral cell toward the end of embryonic development, (2) the immature GL migrate from the lamina propria into the epithelium to differentiate, mature, and proliferate, and (3) the immature GL have specific functions during the neonatal period.