How T Cells Penetrate the Central Nervous System

Autoimmune diseases are among the most dangerous kind in the world. They manifest themselves when the body's own immune system begins to attack the central nervous system (CNS), inflicting severe damage, and eventually leading to death. Multiple sclerosis is one good example. Although the barriers that exist between the CNS and other parts of the body seem to be extremely well constructed, a new video shows precisely how T cells, an important part of the immune system, go through these defenses, and start their attacks.

In the new investigation, a team of scientists from the University Medical Center Institute for Multiple Sclerosis Research, in Gottingen, Germany, managed to track down the movements of the T cells inside a mouse model, and got a chance to look at how they passed through the barrier surrounding the CNS. The research was led by Alexander Flugel, who is also the director of the Institute, Nature News reports. “There's a question about how immune cells that attack the brain get entry because [it] is shielded by the blood-brain barrier,” he says.

In order to get the best possible view of how these cells acted, the researchers tagged disease-causing T cells with green fluorescent proteins, and then injected the batch into the veins of rats. They then used infrared lasers, and a technique known as two-photon imaging, to get a clear view of how the cells were behaving when met by the CNS barrier. The study revealed how the T cells passed through the defenses, and triggered the formation of experimental autoimmune encephalomyelitis, the equivalent of multiple sclerosis in animal models. Details of the team's research appear in the latest issue of the respected scientific journal Nature.

The study has also reshaped some of the knowledge that current textbooks hold, which states that T cells move into the CNS by means of attaching themselves to blood cells. The investigation has revealed that, in fact, they crawl through the blood vessels, and also that they can stop and move backwards, as in upstream. They can exit the blood stream at certain points, and continue to navigate the outside of the blood vessel until they meet with a type of blood cells called phagocytes. When that happens, they start entering the CNS and trigger autoimmune diseases.