Inflammation up-regulates activin B and hepcidin transcription in the absence of IL-6. Groups of C57BL/6 Il-6−/− and Il-6+/+ mice were injected with LPS (1 μg/g of body weight) or saline (5 mice/group) and were killed 4 hours later. (A) mRNA levels of Inhbb and Hamp were measured by quantitative RT-PCR. Values shown are means of −ΔCt (ie, −[Ct target gene − Ct Hprt]) ± SD. Four hours after LPS administration, Inhbb mRNA levels were increased on average 35-fold both in Il-6−/− mice (−ΔΔCt = −3.15 + 8.27 = 5.12; 2−ΔΔCt = 35.10) and in Il-6+/+ mice (−ΔΔCt =−3.26 + 8.39 = 5.13; 2−ΔΔCt = 34.75). Hamp mRNA levels were increased on average 3.1-fold in both Il-6−/− mice (−ΔΔCt = 7.90-6.27 = 1.63; 2−ΔΔCt =3.10) and Il-6+/+ mice (−ΔΔCt = 8.02-6.38 = 1.63; 2−ΔΔCt = 3.10). The effect of LPS on Inhbb and Hamp gene expression was assessed by the Student t test. **P < .01; ***P < .001. (B) Protein extracts were prepared from the mouse livers of the Il-6−/− mice injected with LPS or saline. Phospho–Stat-3, total Stat-3, phospho–Smad1/5/8, and total Smad5 were detected by immunoblot techniques. Densitometry was performed using the ImageJ gel-analysis method and results are shown in supplemental Figure 6.