How a special immune system protects grey matter

Researchers once thought that the brain was walled off from the rest of the body’s immune system, but an exciting picture is emerging of the brain as a unique immunological ecosystem. The brain’s border control actually does allow immune cells from the body into the fluid-filled membranes that surround the organ. Special immune cells produced in the skull’s bone marrow could be gentler than normal immune cells. Researchers are exploring how these and other kinds of immune cells in the brain play a role in fighting diseases and could be harnessed in treatments.