TLR3 agonist poly I:C induction of TNFα in mouse serum and brain. Levels of proinflammatory cytokine TNFα were determined following a single poly I:C (250 μg/kg, i.p.) and d-galactosamine (D-GalN, 20 mg/kg, i.p.) injection into C57BL/6 mice. At the time points indicated, mice were sacrificed and brain extracts and sera prepared as described in methods. Note both brain and serum TNFα peaked at three hours. Interestingly, blood (serum) TNFα declined to control level by 24 hours whereas brain TNFα level remained elevated at about half the peak level for at least 72 hours. The results shown are the means ± SEM of two experiments performed with seven mice per time point. *P <0.05, **P <0.01, compared to the corresponding vehicle controls.