MICROGLIA - MECHANISMS OF ACTIVATION AND INVOLVEMENT IN THE PATHOGENESIS OF NEUROPSYCHIATRIC DISEASES

Microglia are the resident macrophages of the brain. They are the cent ral cellular element to initiate defense mechanisms against destructiv e environmental influences and to facilitate regenerative processes. N o other cell type of the brain is endowed with a comparably comprehens ive, immunocompetent machinery like microglia. It encompasses cell pro liferation, migration and differentiation into full-blown macrophages able to present antigen and to phagocytose cell debris. Relatively lit tle is known about these stages of microglia activation on the cellula r and molecular level, although microglia have been described as a sep arate cell type of the brain as early as in the 30ies of this century by P. del Rio Hortega. This review summarizes the data that have accum ulated until now in this respect and tries to embed them into a clinic al framework. Special focus has been given to the role of this cell ty pe in the development and progression of Multiple Sclerosis, HIV-assoc iated dementia and Alzheimer's disease.