Isolation and Characterization of Brain Macrophages from the Central Nervous System of Newborn and Adult Rats and of Rats with Experimental Allergic Encephalomyelitis

Abstract

A method has been developed to isolate brain macrophages (MΦ) from normal neonatal and adult rat brain cell suspensions, as well as from brain cell suspensions of rats with experimental allergic encephalomyelitis (EAE), by making use of the ability of MΦ to adhere to plastic surfaces.The isolated adherent cells were immuno- and enzyme-cytochemically identified.Phagocytic activity and the presence of Fc-IgG receptors were also examined.Approximately 30%–40% of the isolated adherent cells from neonatal rat brain are phagocytic and can be stained with macrophage-specific monoclonal antibodies, suggesting that these cells belong to the monocyte/macrophage lineage.From normal adult rat brain, only a small number of brain MΦ could be isolated. A highly purified population of brain MΦ was obtained from EAE rat brain.The isolated brain MΦ are phagocytic, possess Fc-IgG receptors and rat MΦ-associated antigens.Besides these features, the isolated brain M(D also express MHC class II antigens (Ia-antigens), which suggests that MΦ may be involved in the regulation of immunological disorders of the CNS. The method reported here for rapidly isolating a large number of blood-monocyte-derived brain MΦ from neonatal and adult brain allows an investigation of the precise role of MΦ in inflammatory diseases of the central nervous system.