PROGRESSIVE ACTIVATION OF ADULT MICROGLIAL CELLS IN-VITRO

Bulk-isolated microglial cells from the adult rat brain grown in N2 me dium supplemented with 10% fetal calf serum survived for at least 2 we eks, and their purity was > 99% at day 1 and > 93% at day 7. The pheno type of freshly plated cells was comparable to that of ''resting,'' ra mified microglia in vivo. With time in culture and with different sche dules, depending on the parameter considered, microglia acquired antig enic (e.g., positivity for vimentin, ED1, major histocompatibility com plex class I antigens, leukocyte common antigen, and to a lesser exten t CD4) and functional (e.g., proliferation, phagocytosis) features cha racteristic of ''activated'' microglia as described in situ. Productio n of nitrite and prostaglandin E(2) in response to lipopolysaccharide increased greatly with time in culture. Phagocytosis was also accompan ied by increased release of nitrite and prostaglandin E(2), the latter being more affected than the first by the age of the cultures. The cu lture system described may be suitable to study the factors that can m odulate ''activation'' of adult microglia. (C) 1996 Wiley-Liss, Inc.