In the brains of people that suffer from long-term multiple sclerosis (MS), inflammatory cells are not entering the brain via the bloodstream anymore. Instead, the cells arise from local memory cells in the brain. Nina Fransen and her colleagues of the NIN indicate this in a recently published article in the scientific magazine 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 inflammation. In patients with advanced MS, the number of attacks of 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. This is remarkable”, says Nina Fransen. The researchers therefore wondered whether white blood cells still play a role in the inflammation during advanced MS.
White blood cells
In this study, the research group of professor Inge Huitinga focussed mainly on one specific type of white blood cell, the T cell. Brain tissue that was donated by MS patients that passed away, was examined at the Netherlands Brain Bank. In this tissue, the researchers found activated T cells inside of 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. In the brain, these cells have only recently been discovered by the same research group.
These new findings support the idea that during the late phase of MS, the disease is happening entirely inside of the brain. In this case, white blood cells outside of the brains do not influence the disease anymore.
“These data give us insight into the poor and disappointing effects of current treatments during later stages of MS. By mapping the behaviour of the T cells, we can start thinking of ways to slow down the disease process in patients with advanced MS”, explains Joost Smolders, member of the research group and neurologist at Erasmus MC in Rotterdam.
In people with MS, inflammation in the brain is responsible for the breakdown of myelin, the insulating layer that forms around nerves. Without this insulation, it would not be possible for nerve cells to communicate properly with each other. As a consequence, important functions like walking, feeling, talking and thinking are being affected. Each person with the condition is affected differently and the course of the disease is hard to predict. Unfortunately, there is no cure for MS yet.
This study was sponsored by the Dutch MS Research Foundation and the participants of the VriendenLoterij.