Figure 1.

Three-level interaction of migratory autoimmune T cells with the blood-brain barrier. Blood-borne T cells attach to the inner surface of a CNS associated blood vessel, where they crawl randomly, but mainly against the blood stream (Level I). The T cells cross the vessel wall and continue crawling on the outer surface (Level II), until they make contact with local perivascular phagocytes. These phagocytes present local autoantigens and signal the migratory T cells to enter the CNS parenchyma (Level III). [Adapted from ²⁷]