A massive genetics study suggests that in multiple sclerosis, the immune system isn’t the whole story—cells inside the brain and spinal cord may help set the pace of disability. One tiny DNA change points to a surprising question: what if “severity” is partly about nervous-system repair, not just inflammation? For years, the dominant assumption in MS has been that if you can calm the immune attack, you can largely control the disease—especially the relapses people feel as sudden flare-ups. But m