Résumé
Macrophages in 14 human livers from 5 to 37 weeks of gestation were studied immunohistochemically and transmission electron microscopically with 3 human fetal livers during the high activity of hepatic hemopoiesis. Author had used a highly specific mAb, CD68 to examine the distribution of mature macrophages in human fetal livers, with special reference to their presence in the hemopoietic microenvironment. Kupffer cells and macrophages were first seen in human enbryos by 7 weeks of gestation in primitive hepatic sinusoids and hepatic laminae. Thereafter numbers of CD68 labelled cells increased concomitantly with the rapid expansion of hemopoietic activity. From 11 to 26 weeks of gestation, the human fetal livers showed the maintenance of high hemopoietic activity and erythroblastic islands with various shapes. Macrophages in human fetal livers formed part of the hemopoietic stroma and their extensively spread plasma cytoplasmic processes, could be seen making intimate contacts with clusters of developing erythroblastic cells. Partly macrophages in the erythroblastic islands contained several developing erythroblastic cells (emperipolesis). Studies using the electron microscope demonstrated intact membranes surrounding the developing erythroblastic cells and lining the macrophagic vesicles. The decline of hepatic hemopoiesis after 27 weeks of gestation coincided with the decline of the size of an erythroblastic island and the disappearence of macrophage in the erythroblastic islands. The above results suggest that macrophages in the hepatic hemopoiesis participate in non-phagocytic hemopoietic cell interactions, erythroblastic island and macrophagic emperipolesis, as well as in phagocytosis of erythroblastic nuclei and dying cells.