Infections and blood-brain barrier [İnfeksiyonlar ve Kan-Beyin Engeli]

Brain functions are protected by blood-brain barrier,which is a specialised structure consisting of endothelial cells and tight juctions between them,a continuous basal lamina which surrounds these cells. the tight junctions are reinforced by the foot processes of the astrocytes. the protective effect of blood brain barrier is however,lost during bacterial,viral,fungal or parasitic infections. the exact mechanism by which microorganisms pass through the blood-brain barrier is moreover,not adequately known. however,the principal mechanisms could be increased permeability of the blood brain barrier and/or direct invasion of microorganisms to brain. microorganisms enter the central nervous system through transcellular penetration,paracellular entry and transmigration with infected leukocytes. furthermore,astrocyte activation and enhanced neuronal apoptosis due to astrocyte activation during infection can cause neuronal loss. this review aims to discuss the mechanisms of blood brain barrier alterations during central nervous system infections.