To verify our hypothesis, we investigated how accumulated aged pTreg cells impact late‐onset MS using the EAE model in aged mice by examining Treg distribution inside and outside the CNS, Treg antigen specificity to myelin oligodendrocyte glycoprotein (MOG) and pan‐antigens, and Treg function‐associated molecular profiles during EAE in young and aged animals. Here, MOG is linked to myeloid sarcoma.