Localization of plasmacytoid cells and DCs in the human thymus.

Plasmacytoid cells are both in the cortex and the medulla; mature DCs are localized in the thymic medulla. (A) Mature DCs expressing high levels of CD40 (in blue) are localized in the medulla (M) identified by the presence of Hassall corpuscles (HCs). (B) A closer view of the corticomedullary junction shows that round red IL-3Rα⁺plasmacytoid cells (black arrows) are found in the cortex and are found in the medulla near blue dendritic CD40^highmature DCs (empty arrows). (C) In the medulla, blue CD86^high DCs (empty arrows) are surrounded by red IL-3Rα⁺ plasmacytoid cells (black arrows). No blue CD86^high DCs was found to coexpress the IL-3Rα. M indicates medulla; C, cortex; T, trabeculae; HC, Hassall corpuscles. Original magnification: 100 × (panel A); 400 × (panels B and C).