In a small trial, immune cells that fight the Epstein-Barr virus have stopped the progression of multiple sclerosis, an autoimmune condition that can lead to symptoms, such as difficulty walking, that worsen over time
Source: MS reversed by transplanted immune cells that fight Epstein-Barr virus | New Scientist
Yes, a small trial, but still … a very encouraging result. (Looks like a hard paywall, sorry. But the summary alone seems pretty exciting.)