IL-6 suppresses HBV replication in a dose-dependent manner. (A) 1.3ES2 cells were treated 6 days after plating (when the cells had reached confluence) with various doses of IL-6 (0, 5, 10, 20, 40 ng/ml). The cell lysates were harvested after 4 days treatment with IL-6 and equal amounts of sample were analyzed by particle blot analysis using native agarose gel electrophoresis. HBV genome-containing nucleocapsids were detected by Southern blot analysis of the disrupted nucleocapsids, using an HBV-specific probe. Expression of β-actin was used as an internal control for sample loading. The signals were quantified by densitometry analysis and expressed as percentage of the control cells to indicate the inhibitory effect of IL-6. (B) Effect of IL-6 on growth curve. The cells were treated with IL-6, as described above. The cell number was determined by the trypan blue exclusion method.