Maturation and activation of BMDCs stimulated by rHuN4-GM-CSF. BMHCs as DC precursors were cultured with or without GM-CSF. The cells were infected with viruses. LPS and GM-CSF were used as a positive control, and the medium from untreated cells (Mock) served as a negative control. Maturation of BMDCs treated by GM-CSF and then inoculated virus at 48 hpi (A). Activation of BMDCs were cultured without GM-CSF, but directly infected with viruses at 48 hpi (B) and 72 hpi (C). All data are the means from three independent experiments with cells from different donors. The horizontal lines represent the geometric mean for each group, and statistical analysis was performed. *: P < 0.05; **: P < 0.01.