Injecting extracellular vesicles from healthy mice into mice that had an MS-like disease resulted in the development of a relapse-remitting disease and active CD8+ cells, similar to that seen in human patients with multiple sclerosis. Examining the EVs in mice and humans with MS, researchers identified they contained fibrinogen, a protein normally associated with blood clotting and wound healing. According to researchers, the EVs with fibrinogen appear to activate the CD8+ immune cells. The findings could help with the development of new treatments for RRMS.