CD4(+) T cells from multiple sclerosis patients respond to a commensal‐derived antigen

Multiple sclerosis, an immune‐mediated disease of the central nervous system, is characterized by the impaired function of regulatory cells that fail to suppress self‐reactive effector cells. We have previously found that polysaccharide A, a capsular antigen derived from the human gut commensal Bacteroides fragilis, can induce a population of regulatory T cells. Herein, we demonstrate that naïve T cells isolated from patients with multiple sclerosis have the capacity to acquire regulatory characteristics when stimulated in vitro with polysaccharide A. This study demonstrates the amplification of a regulatory T cell response by a gut‐derived commensal antigen in those with multiple sclerosis.