The blood-brain barrier (BBB) is a dense patchwork quilt of vessels that serve as gates, regulating the passage of substances, like bacteria, chemicals, and drugs, from the blood to the brain. Researchers have discovered that the BBB does allow for certain B-cells and T-cells to squeeze through, in a process called diapedesis, to do regular “checkups.” But this was no routine checkup. The immune cells it had let through, which were supposed to protect the body, were in mid-blitz. This was the evidence Dr. Najjar had needed: I was in the grip of some kind of autoimmune disease.
