Inflammation dramatically increases the transcription of activin B, but down-regulates that of activin A, even in the absence of Bmp6. Groups of 6 CD1 mice (3 wild-type and 3 Bmp6^−/−) were killed at different time points after administration of LPS (1 μg/g of body weight). mRNA levels of Inhbb, coding for the β_B activin subunit (A), and Inhba, coding for the β_A activin subunit (B), 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 more than 35-fold in both wild-type (−ΔΔCt = −3.29 + 8.43 = 5.14; 2^−ΔΔCt = 35.26) and Bmp6^−/− mice (−ΔΔCt = −3.85 +9.44 = 5.59; 2^−ΔΔCt = 48.16). Effect of LPS on target Inhbb or Inhba gene expression independently of the mouse genotype was assessed by 2-way ANOVA. ***P < .001; **P < .01).