BG induces immune training in microglia 2 days after injection. a Diagram of preconditioning experimental design with 2-day interval. Mice were first challenged with PBS, LPS (1 mg/kg) or BG (20 mg/kg) by i.p. injection on day 0. On day 2, all the mice received a second stimulation of PBS or LPS (1 mg/kg). Animals were terminated 3 h after the second injection. b Microglia were isolated and gene expression levels of Tnf, Il1β, Ccl2, Ccl3, Il6 and Csf1 were determined using qPCR and normalized to Gapdh gene expression levels (n = 4 mice). c Gene expression levels of Dectin-1 and Tlr4 were determined by qPCR and normalized to Gapdh gene expression levels (n = 4 mice). The significance was calculated by one-way ANOVA followed a Bonferroni correction for multiple comparisons. *, p < 0.05; **, p < 0.01; ***, p < 0.001.