Effect of LPS prestimulation on cytokine production after a second challenge with antigen, a TLR2 agonist (P3C), or a combination of both. BMMC were prestimulated with LPS (100 ng/ml) for 18 hours. Next, the cells were stimulated with 20 ng/ml Ag, 1 μg/ml P3C, or a combination of both for 24 hours for analysis of the production of cytokines. Reduction of TNFα (A) and IL-6 (B) production was seen after stimulation with P3C alone (* TNFα p = 0.047; * IL-6 p = 0.029) and in combination with Ag + P3C (* TNFα p = 0.012; * IL-6 p = 0.004), but not with Ag alone (p > 0.05), suggesting a cross-tolerance effect linking TLR2 and TLR4 agonists. Values are mean and SEM from 3 independent experiments.