Ultrastructural effects of sex hormones and infection on lymph node post-capillary venules

The ultrastructure of the lymph node post-capillary venules (PCV) was studied in control, gonadectomised and gonadectomised-Hexoestrol treated male and female mice, infected or not with Toxoplasma gondii. The percentage of the cytoplasmic area of the endothelial cells occupied by Golgi apparatus was estimated by quantitative stereology. The endothelial cells of the PCV are higher and contain more Golgi elements in female than male controls. Oophorectomy decreases the percentage of Golgi apparatus and the height of the endothelial cells while orchidectomy does not affect the former but increases the latter. The endothelial cells react to Hexoestrol similarly in male and female mice, by increasing their height and becoming more heavily structured, with an effect particularly on the Golgi apparatus. All groups of mice infected with Toxoplasma gondii, show increased numbers of lymphocytes passing through the wall of the PCV. The endothelial cells of the latter show increased numbers of ribosomes both free and attached to rough endoplasmic reticulum. Golgi elements are decreased. In view of these findings the mechanisms for selective lymphocyte migration through the walls of the PCV are discussed.