By the time most people go to the doctor with symptoms of multiple sclerosis (MS), their brain has already been under attack for years.
Until now, scientists didn’t fully understand when the damage started or which brain cells were affected first.
But a new study from researchers at UC San Francisco has changed that. They looked at thousands of proteins in people’s blood and found the earliest signs of MS, giving them a clearer picture of how and when the disease begins. Their findings were published in the journal Nature Medicine.
MS is a disease where the body’s immune system attacks the brain and spinal cord. One of the first things it destroys is the myelin sheath—a fatty layer that covers and protects nerve fibers.
Without this protection, the nerves can’t send signals properly, leading to the symptoms of MS like weakness, balance problems, and vision loss. A year after the myelin breaks down, the nerves themselves begin to show damage.
To study how MS starts, researchers used blood samples from the U.S. Department of Defense Serum Repository, which stores blood from military service members. These samples allowed scientists to go back in time—some of them were taken many years before the donors were diagnosed with MS.
They studied blood samples from 134 people who later developed MS and found something remarkable. Seven years before diagnosis, there was a rise in a protein called MOG, which signals damage to the protective myelin sheath. About a year later, another protein called neurofilament light chain appeared, showing damage to the nerve fibers themselves.
They also found high levels of a protein called IL-3, which helps call immune cells into the brain and spinal cord. IL-3 appears early—before symptoms even start—and may be one of the key players in triggering the immune system’s attack on the brain.
In total, the team found about 50 proteins that could serve as warning signs for MS. They’ve filed a patent for a new blood test that uses the top 21 of these proteins to help predict who may develop MS in the future.
Dr. Ahmed Abdelhak, one of the lead researchers, said this discovery could change the way doctors diagnose and treat MS. With earlier detection, it might be possible to slow or stop the disease before it causes serious damage.
Dr. Ari Green, another senior researcher on the team, said the study offers hope—not just for better treatments, but for prevention. He explained that knowing MS begins long before symptoms appear gives doctors a chance to protect people earlier and prevent permanent brain damage.
This study is a major step forward in understanding MS. It shows that the disease begins quietly, years before patients notice anything is wrong. It also opens the door to blood tests that could help find and treat MS sooner. With this knowledge, doctors may one day prevent MS or stop it from getting worse.
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The study is published in Nature Medicine.
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