Primary cell cultures of C57BL/6 cerebral cortex are enriched in astrocytes. CNS cells of seven to ten days of primary culture were seeded at a density of 105 cells per 13-mm-diameter coverslip and analyzed 24 h later. (a, b, c) Giemsa staining reveals cells resembling astrocytes with thin extensions, delicate branches, recognizable nucleoli and cytoplasm lightly stained. (d, e, f) Simultaneous immunohistochemical staining for GFAP and CD11b was used to determine the cell composition of primary astrocyte cultures. (e) Insert showing RAW 264.7 mouse macrophage lineage used as positive control for CD11b staining. (TIFF 1266 kb