[The ultrastructure of Langhans cells in pathologic human placentas (author's transl)]

In electron microscopic observations on the villous cytotrophoblast in pathologic human placentas we find, besides a general increase of the amount of Langhans cells, significant ultrastructural differences according to the different diseases in pregnancy. Diabetes mellitus: the most striking observations are small, extremely electron dense mitochondria and a lot of intracellular filaments in a hydropic cytoplasm. Rh-incompatibility: according to the stage of placental damage the Langhans cells show a different structure. In light cases we find hydrolic cells with normal mitochondria as well as swollen ones. The plasmalemm shows a lot of foldings and dentations with the syncytium. In serious cases of rh-incompatibility the Langhans cells cover the trophoblastic basal membrane completely. Their electron density is even higher than that of the syncytium. Characteristic lysosomes appear. In the most serious cases the syncytium is completely destroyed and maximal hydropic Langhans cells cover the villi. EPH-gestosis: the Langhans cells show different phases of differentiation, but no other characteristic criteria. The importance of the Langhans cells for the regeneration of the syncytotrophoblast is discussed. Mitochondria and rough endoplasmic reticulum are obviously not formed in the syncytium but they must be regenerated by taking up Langhans cells by syncytial fusion.