A treatment involving a combination of chemotherapy and stem cell transplantation has kept 49 of 52 multiple sclerosis (MS) patients in remission for three years.
The exact cause of MS is unclear; genetic and environmental determinants are hazy, and yet more than 2.3 million people are afflicted by MS worldwide, and women are twice as likely to develop MS than men in their lifetime, according to the National MS Society .
The name “multiple sclerosis” refers to lesions that develop on the brain and spinal cord of patients. These lesions occur when myelin, a white, fatty coating that insulates the body’s nerves, is mistakenly labeled as a foreign invader, attacked, and stripped from the nervous system by the immune system. Without insulation, neurons lose their important ability to conduct electrical signals, resulting in trouble with sensation, blindness, muscle weakness, and loss of coordination.
Although the exact trigger for MS is poorly understood, researchers have noticed that once an MS patient’s immune cells mistakenly target myelin, the old immune cells influence new immune cells to perpetuate the disease-causing mistake.
This new treatment attempts to reset the immune system’s mistake, by interrupting the line of communication between old (defective) and young (naïve) immune cells.
First, immune system stem cells are removed from the MS patient’s bone marrow. With young immune cells set aside for safe-keeping, the patient then undergoes extensive chemotherapy to destroy their old immune cells—including the ones spawning MS inflammation. Once the previous immune system is destroyed, the body is repopulated with the young immune cells that had been set aside at the beginning of the procedure. Since the immature cells seem to represent the patient’s immune system before MS-related mistakes were triggered, the end result is akin to an immune-system reset.
The process is not trivial—chemotherapy itself is a taxing process, and because the immune system is virtually decimated, patients must endure weeks in isolation to avoid illness. However, once the immune system is reset, myelin insulation finally has time to regenerate (via special cells called oligodendrocytes), and the body can recover.
Image credit: Zeynep Saygin