Glial cells. Computer generated image showing co-localisation of tau proteins (red) and IL6 (interleukin 6, green) cytokine proteins in glial cells (neuroglia). Glial cells are non-neural cells of the central nervous system (CNS, brain and spinal cord). They are the predominant cell type in brain tissue and are thought to outnumber neurons by 10 to 1. Their precise roles are not well understood but they are thought to provide physical and functional support to neurons (nerve cells) and to participate in maintenance of the blood-brain barrier by attachments to blood vessels (as seen here). Magnification: x1600, when printed 10 cm wide.