T lymphocytes infiltration and inflammatory mediators at the blood-cerebrospinal fluid barrier (BCSFB) in AD. The BCSFB is a selective barrier that restricts the passages of circulating immune cells from the stroma compartment into the brain parenchyma. In AD the BCSFB is impaired and T cells migrating through the BCSFB produce inflammatory mediators which are associated with the immune response to pathological conditions. At the BCSFB the chemokine CCL11 is produced in response to IL-4 secreted from Th2 cells and can be inhibited by IFN-γ secreted from Th1 cells. In the CSF in AD the increased levels of cytokines: TNF-α, IL-6, IL-8, chemokines: CXCL8, CCL11, and CCL2, and cytokine receptors: sIL-6R, TIMP-1, and TNFR-I are observed. Moreover, enhanced expression of ICAM-1, VCAM-1, and P-selectin in the CPE leads to the damage of tight junctions and modulates immune cell migration to the CSF. Additional explanations can be found in the article text. Bold arrows indicate regulation of molecule levels [↑, upregulation, ↓, downregulation]. Blue arrows indicate affected processes.