Nerve cell response to brain injury. Fluorescent light micrograph of a section through an injured brain. Glial progenitor cells are green and reactive astrocytes, a type of glial (support) cell are red. It is thought that reactive astrocytes restrict inflammation at the site of an injury and protect other nerve cells, helping to limit tissue degeneration. However, their accumulation can also cause the formation of destructive scar tissue. Glial progenitor cells are immature cells that can differentiate into any of the different types of glial cell.