Effect of rIL-1β, rIL-6, and rTNFα on FXII synthesis by HepG2 cells. HepG2 cells were grown to 80% confluence in 24-well plates and incubated under serum-free conditions with 50 ng/mL of rIL-1β, rIL-6, rTNFα, and a combination of rIL-1β and rIL-6 for 72 hours. Culture medium was refreshed every 24 hours. FXII concentration in culture media obtained after the third 24-hour period was measured by ELISA as described in the Materials and Methods. Results represent the mean ± SD of three independent experiments. *P < .05 as compared with unstimulated cells.