Local T Cells Invade the Late-Stage MS Brain

In a study published yesterday in Brain, researchers from the Netherlands Institute for Neuroscience have discovered new information regarding multiple sclerosis (MS) and inflammatory cells. It turns out, in the brains of people that suffer from long-term multiple sclerosis (MS), inflammatory cells no longer enter the brain via the bloodstream. Instead, the cells arise from local memory cells in the brain.

At its onset, MS is characterized by a relatively high frequency of attacks of neurological symptoms that recover relatively well. During attacks early in the disease, white blood cells migrate from the bloodstream into the brain, where they contribute to the inflammation. In patients with advanced MS, the number of attacks with neurological symptoms is reduced, but disability does progress.

“Our previous studies indicated that there is still a significant amount of inflammatory activity in the brain also at later stages of MS, which is remarkable,” says first author Nina Fransen. The researchers therefore wondered whether white blood cells still play a role in the inflammation during advanced MS.

The researchers focused mainly on one specific type of white blood cell: the T cell. They examined brain tissue that was donated by MS patients who passed away and found activated T cells inside the inflammatory lesion centers. These cells had characteristics of tissue-resident memory T cells. This kind of T cell remains in tissues after viral infections and offers long-term local protection to new infections.

According to the new data, the late phase of MS occurs exclusively inside the brain; white blood cells outside the brain no longer influence the course of the disease. “These data give us insight into the disappointing effects of current treatments during later stages of MS,” says co–corresponding author Joost Smolders. “By mapping the behavior of the T cells, we can start thinking of ways to slow down the disease process in patients with advanced MS.”