MicroRNA-155 modulates Th1 and Th17 cell differentiation and is associated with multiple sclerosis and experimental autoimmune encephalomyelitis.

Mammalian noncoding microRNAs (miRNAs) are suggested to be involved in immune system function. We found that miR-155 expression was highly correlated with disease severity in patients with multiple sclerosis and mice with experimental autoimmune encephalomyelitis (EAE). Knockdown of miR-155 resulted in low Th1 and Th17 cells and mild EAE, and its overexpression led to more Th1 and Th17 cells and severe EAE. MiR-155 promoted the development of inflammatory Th17/Th1 cell subsets. These findings demonstrate that miR-155 confers susceptibility to EAE by affecting inflammatory T cell responses and can be a new target for therapy of multiple sclerosis.