AFFERENT MIGRATION OF THE KURLOFF CELLS VIA LYMPHATICS INTO THE THYMUS OF ESTRADIOL-TREATED GUINEA-PIGS

The spatial distribution and migration of Kurloff cells containing PAS -positive large inclusion bodies in the thymus of estradiol-treated gu inea pigs were histochemically studied by a combination of light and e lectron microscopy. Male guinea pigs mere examined at various interval s from 7 days to 3 months after a single subcutaneous injection of est radiol. Differentiation of lymphatics from blood capillaries was perfo rmed by a 5'-nucleotidase (5'-Nase) staining method and the occurrence of Kurloff cells within 5'-Nase-positive lymphatics was confirmed by ultrastructural histochemistry. Several Kurloff cells first appeared a t 7 days within lymphatics in the thymic capsule or interlobular conne ctive tissues. At 12-15 days after estradiol administration, a lymphat ic accumulation, a so-called ''lymphatic center'', was seen in the thy mic septa even though few Kurloff cells were present within the thymic parenchyma. The ''lymphatic center'' contained many Kurloff cells loc ated in its periphery and in the surrounding marginal sinus which comm unicated with the thymic interlobular lymphatics. At 21 days after est radiol, Kurloff cells were preferentially accumulated along the cortic omedullary junction extravascularly. Later the distribution was more d iffuse. The conspicuous accumulation of Kurloff cells in the corticome dullary region could reflect an inability of Kurloff cells to use bloo d vessels as a route for migration. These findings strongly suggest th e afferent migration of Kurloff cells into the thymus via lymphatics.