Methylprednisolone attenuates interferon-β induced expression of HLA-DR on monocytes

The effect of methylprednisolone on constitutive and interferon-β(IFN-β) induced HLA-DR expression on monocytes from multiple sclerosis (MS) patients was investigated. Constitutive HLA-DR expression was reduced by 50% following a single dose(500 mg) of intravenous methylprednisolone (IVMP). Stimulation with natural IFN-β, in vitro, resulted in a 20 fold increase in HLA-DR expression. Following IVMP, IFN-β inducible HLA-DR levels were reduced (non-significantly) by 20–30%. Experiments in which monocytes from normal subjects and MS patients were pre-treated in vitro with methylprednisolone prior to IFN-β stimulation revealed that induction of HLA-DR was significantly inhibited; in contrast, IFN-β induced HLA-DR expression was not down-regulated following subsequent in vitro treatment with methylprednisolone. These findings suggest that the immunomodulatory effects of IVMP could be attenuated in MS patients receiving regular IFN-β therapy.