Decreased Dicer expression is linked to increased expression of co-stimulatory molecule CD80 on B cells in multiple sclerosis

Background: Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the central nervous system. B cells have been strongly implicated in disease pathogenesis based on clinical trials with B-cell ablation. There is a growing body of evidence linking microRNAs with regulation of the immune system. Dicer, a key enzyme involved in microRNA biogenesis, is necessary for normal B-cell function. Objective: We aimed to determine whether Dicer expression is impaired in B cells and is linked to increased expression co-stimulatory molecules in patients with MS. Methods: B cells were separated from blood samples of MS patients and healthy subjects. Expression of Dicer and co-stimulatory molecules CD80 and CD86 was tested. The effect of Dicer modulation on CD80 and CD86 expression in B cells was studied. Results: Dicer expression was decreased in B cells but not in monocytes of patients with MS compared with healthy subjects. CD80 and CD86 expression was increased on B cells of MS patients compared with healthy subjects. Inhibition of Dicer expression in B cells by small interfering RNA led to increased expression of CD80. Conclusion: Dicer expression is decreased and is mechanistically linked to increased expression of co-stimulatory molecule CD80 in B cells of patients with MS. This may contribute to activation of immune responses in MS.