BACKGROUND: The use of methylprednisolone (MP) is still controversial for hepatitis B virus related acute-on-chronic liver failure (HBV-ACLF). We aimed to explore the change in dendritic cells (DCs) during MP treatment in HBV-ACLF to guide the use of MP to improve patient's prognosis. METHODS: Patients with HBV-ACLF were prospectively allocated to groups given methylprednisolone intravenously (1.5 mg/kg/day for the first 3 days, 1 mg/kg/day for the second 2 days, and 0.5 mg/kg/day for the last 2 days, MP group, n = 36) plus standard treatment or standard treatment only (CM group, n = 34). The phenotype [myeloid and plasmacytoid DCs (mDCs, pDCs)] and function of DCs (IL-12 and IFN-α production) were measured at baseline (0d), 3d, 7d, 10d, 14d, 28d, and then monthly until 3 months. Patients' survival was assessed until day 90. RESULTS: The 3-month survival rate was significantly higher in the MP group than the control (72.0 % vs. 35.5 %，P <
0.01). The phenotype and function of DCs were suppressed in the MP group. The mDCs counts was lower in non-survivors compared to survivors at baseline. Patients with a decline in mDCs counts at the 7th day and a continuous increase in mDCs counts from the 10th day presented a better outcome for patients with MP treatment. Bilirubin was the only relative factor for the restoration of mDCs in the MP group (odds ratio, 0.991
95 % confidence interval, 0.984-0.999
P = 0.023). CONCLUSIONS: Methylprednisolone could improve the outcome of HBV-ACLF by inhibiting the circulating mDCs counts. And the recovery of mDCs counts after methylprednisolone treatment could represent a favorable response. We can consider monitoring the circulating DCs counts to guide the use of MP in HBV-ACLF in order to improve patient outcomes.