Astrocytes

Astrocytes, a kind of glial cell, are the primary support cells of the brain and spinal cord. They make and secrete proteins called neurotrophic factors. They also break down and remove proteins or chemicals that might be harmful to neurons (for example, glutamate, a neurotransmitter that in excess causes cells to become overexcited and die by a process called excitotoxicity).

Astrocytes aren't always beneficial: After injury, they divide to make new cells that surround the injury site, forming a glial scar that is a barrier to regenerating axons.