Nerve cells. Fluorescent light micrograph of an oligodendrocyte (centre) and a microglial cell (upper left) from a human brain. Cell nuclei, which contain the cell's genetic information, have been dyed blue, membrane cofactor protein, a protein involved in the immune system , is red, myelin/oligodendrocyte specific protein, which is involved in the production of myelin, is green. Oligodendrocytes form the myelin sheath around neurons (nerve cells) in the central nervous system (CNS). The sheath insulates the nerve axon, allowing for faster transmission of electrical impulses. Microglia are involved in immune reactions in the CNS, they recognise areas of damage and inflammation and phagocytose (engulf) cellular debris.