BACKGROUND: YIC (HBsAg complexed with anti-HBs) has been shown to revert immune tolerance in a transgenic mouse model.In phase Ⅰ and Ⅱ clinical trials, YIC induced high titer of anti-HBs in healthy adults, and serum IFN-γ and IL-2 in chronic hepatitis B patients.The highest rates of HBeAg loss (23.1%), HBeAg sero-conversion (21.8%), and higher than 2 log10 decrease in serum HBV DNA (31.2%) were observed in the 60 ug YIC immunized group of chronic hepatitis B patients.The therapeutic mechanism of YIC was predicted to modulate antigen presenting cells by the Fc fragments of anti-HBs in YIC.This study is thus to investigate how YIC modulates dendritic cell (DCs) functions from chronic hepatitis B patients.