Peripheral immune tolerance in LPS- and BG-preconditioned mice. Mice were first challenged with PBS, LPS (1 mg/kg) or BG (20 mg/kg) by i.p. injection. Two days later, the mice received a second stimulation with PBS or LPS (1 mg/kg). Animals were terminated 3 h after the second injection. Sera of mice in the same experimental group were pooled (n = 4 for each group). Cytokine levels were measured with a cytokine array (a). Densitometric analysis of the immunoreactivity of each cytokine or chemokine was performed. After filtering, a heatmap was generated based on optical density levels of cytokines and chemokines (b).