Oligodendrocyte nerve cells. Fluorescent light micrograph of human oligodendrocyte nerve cells. 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. One oligodendrocyte may be responsible for the myelination of up to 50 nerve fibres.