ABSTRACT
The presence of erythroblasts within Kupffer cell was studied for transmission electron microscopically with 5 human fetal livers from 11 to 23 weeks of gestation during the high activity of hepatic hemopoiesis. By using continuous series of thin sections electron microscopically, the objective of the present study was to evaluate the relevance between a migrated erythroblast and a Kupffer cell, and the migration of erythroblasts within Kupffer cells in the sinusoidal lumen. During the examined period the sinusoidal wall consisted of endothelial cells and Kupffer cells, being deficient in basement membrane. Erythropoietic cell-Kupffer cell interaction was often found as the emperipolesis and adhesion between the cells in human fetal liver under electron microscopy. The cytoplasm of the emperipoletic Kupffer cell contained several mitochondria, rough endoplasmic reticuli, clear vesicles, electron dense bodies, cellular debris with shrunken chromatin of enucleated nuclei, intact enucleated nuclei, and erythroblast bearing vacuoles as intact erythroblasts. Intracellular erythroblasts in the Kupffer cell remain unaltered with their normal structure and showed mitosis, enucleation and migration of erythroblast into the sinusoidal lumen. And a clear zone of a vacuole was readily seen around the intracellular erythroblast within Kupffer cell. On occasion, the hypertropic Kupffer cell with interacellular erythroblasts virtually occluded the sinusoidal lining cell. Processing of a migrating emperipoletic erythroblast within a Kupffer cell, the erythroblast migrated via migration pore through the luminal cell membrane of the Kupffer cell into the sinusoidal lumen. An invasion of a proerythroblast into Kupffer cell or a migration of the cell into the sinusoidal lumen had been found in human fetal liver from 11 to 13 weeks of gestation. The results demonstrate that migration of emperipoletic erythroblasts within Kupffer cells occurs in human hepatic hemopoiesis. We suggest that emperipolsis may be one of the mechanisms that support the maturation of erythroblasts in human fetal liver.