<p>Multiple sclerosis (MS) is a neurodegenerative and autoimmune disease affecting the central nervous system (CNS). Recently, mesenchymal stem cells (MSCs) and their extracellular vesicles (EVs) have been extensively studied as a potential treatment for MS. In this study, we examined the impact of therapy using EVs derived from murine bone marrow MSCs (BMSC-EVs) on the proliferation of splenocytes, frequency of regulatory T cells (Tregs), and cytokine secretion in mice induced with experimental autoimmune encephalomyelitis (EAE), comparing the effects with those of their parent cells. After inducing EAE in 30 mice, the animals were divided into three groups and treated with PBS, BMSCs, or BMSC-EVs. The mice were sacrificed on day 30 post-immunization, and their splenocytes were isolated for further analysis. The proliferation of splenocytes was assessed by measuring the fluorescent intensity of CFSE dye using a FACSCalibur flow cytometer, the frequency of Treg cells was determined by flow cytometry, and cytokine levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, IL-10, and transforming growth factor-beta (TGF-β) were measured using enzyme-linked immunosorbent assay (ELISA). The results showed that treatment with BMSC and BMSC-EV both significantly reduced splenocyte proliferation, increased Treg cell frequency, and shifted cytokine profiles toward reduced pro-inflammatory (TNF-α, IL-1β, IL-6) and increased anti-inflammatory (IL-10, TGF-β) cytokines compared to untreated EAE controls, with comparable efficacy between BMSCs and BMSC-EVs. These findings emphasize the capability of BMSC-EVs to serve as a cell-free therapy for immune response modulation in EAE.</p>