Objective To investigate the effect of methylprednisolone on T helper 17 cell (Th17 cells) related cytokines (interleukin (IL)-23,17A,21,22,6,and tansforming growth factor (TGF)-β) in serum and cerebrospinal fluid from patients with relapsing remitting multiple sclerosis and their effects on the pathogenesis.Methods We recruited relapsing remitting multiple sclerosis group (38 patients)and noninflammatory neurological disease group (20 controls),and detected the levels of IL-23,IL-17A,IL-21,IL-22,TGF-β and IL-6 in serum and cerebrospinal fluid (CSF) with ELISA kit in both controls and patients before and after treatment by methylprednisolone.Results After treatment in relapsing remitting multiple sclerosis patients,IL-17A,IL-23,IL-21,and IL-22 levels in cerebrospinal fluid and serum were significantly decreased,however,they were still higher than that in the non-inflammatory neurological disease patients.TGF-β levels was significantly increased (serum:(17.2 ± 5.9) pg/ml vs (34.1 ± 6.5) pg/ml,t =14.351,P =0.000 ; CSF:(26.4 ± 4.7) pg/ml vs (73.2 ± 19.7) pg/ml,t =16.352,P =0.000).The levels of TGF-β in serum and CSF in patients before treatment were lower than those of in non-inflammatory neurological disease patients (serum:(30.2 ± 8.9) pg/ml,t =6.769,P =0.012 ; CSF:(3 1.4 ± 7.5) pg/ml,t =9.368,P =0.017).However,the levels of TGF-β in CSF in patients after treatment were significantly higher than those in non-inflammatory neurological disease patients (t =9.138,P =0.000).Correlation analysis showed that IL-23 and IL-17A were positive correlation in the serum of relapsing remitting multiple sclerosis patients before treatment.Moreover,positive correlations among IL-23,IL-17A and IL-21 were detected in the CSF of relapsing remitting multiple sclerosis patients before treatment.Conclusions Decreased levels of IL-23,IL-17A,IL-21 and IL-22,and elevated levels of TGF-β were detected in serum and CSF of patients with relapsing remitting multiple sclerosis after methylprednisolone treatment.IL-23,IL-17A,IL-21,IL-22 and TGF-β might involve in the pathogenesis of relapsing remitting multiple sclerosis.