Identification of microglia in primary cultures of mixed cerebral cortical cells.

Microglia were investigated in tissue cultures of dissociated cerebral cortex from embryonic rat. Three different forms of microglia were identified in relatively mature cultures on the basis of morphological criteria, esterase histochemistry, and immunohistochemical staining for Fc receptors. Two of these forms corresponded to the amoeboid and ramified microglia; the amoeboid form stained intensely for esterase activity and ramified cells possessed Fc receptors. The third microglial cell form was distinguished by its morphological properties and was characterized by the presence of numerous filopodial processes. This morphological form occasionally possessed esterase staining and was the predominate type of microglia observed in the cultures. The identification of these cell types supports the potential use of this culture system to investigate functional aspects of microglia and their interaction with other brain cells.