Dose-dependent effect of recombinant human cytokines on HAMP promoter activity. HuH7 cells were cotransfected with WT-HAMP promoter-firefly luciferase construct and pTK-RL construct and treated with increasing doses of recombinant human cytokines. After treatment, cells were lysed and luciferase activity was measured. Results for individual cytokines (A-F) are expressed as fold induction over untreated control (firefly/renilla ratio of the experimental condition divided by the firefly/renilla ratio of untreated control). Dots and error bars represent mean ± SD of at least 3 independent experiments executed in duplicate. Statistical significance was determined with the Mann-Whitney rank-sum test, and *P < .05 compared with untreated control.