Effect of ATRA on TF, TNF-α, and IL-8 expression LPS-stimulated THP-1 cells. THP-1 cells (1 × 10⁶ cells) were incubated LPS alone, ATRA (10⁻⁵ mol/L), or various doses of ATRA (1 × 10⁻⁹ to 1 × 10⁻⁵mol/L) before LPS stimulation (10 μg/mL). (A) THP-1 cells were exposed to LPS for 5 hours and TF activity was determined using a one-stage clotting assay. (B) THP-1 cells were exposed to LPS for 24 hours and TNF-α antigen levels in culture supernatants measured by ELISA. (C) THP-1 cells were exposed to LPS for 24 hours and IL-8 antigen levels in culture supernatants measured by ELISA. Results from three independent experiments (mean ± SE) are shown.