[Ultrastructural changes in the dermal blood vessels in patients with psoriasis]

The ultrastructural analysis of psoriatic dermal lesions has shown the alteration of the dermal arterioles into specialized postcapillary venules, the so called high endothelial venules (HEV) which are characterized by the presence of tannic acid staining materials (TASM) located among the endothelial cells. This type of venules seen in the lymphatic nodes and other lymphoid organs is considered to be an important site of lymphocyte recirculation. Similar venules are seen in the lymphatic nodes too. In correlation with the immunologic evidences in the lymphoid tissues and in psoriasis most probably in question are the identical surface antigen-lymphocyte receptors on the HVE which support selective binding of the definite subset of lymphocytes and migration from blood to tissues.