Dose- and time-dependent activation of caspase-1 and induction of IL-1β secretion by LPS in the monocytic cell line THP-1. DH-VD₃–pretreated THP-1 cells were stimulated with increasing concentrations of LPS (S minnesota Re595) as indicated. (A) Cells were lysed at the time points indicated and caspase-1 activity was assessed as described in the Materials and Methods. (B) In parallel, cell-culture supernatants were collected and assayed for IL-1β by ELISA. Shown are mean values of three independent experiments ± SD. (×) Without LPS; (□) 1 ng/mL LPS; (•) 10 ng/mL LPS; (▵) 100 ng/mL LPS; (▪) 1,000 ng/mL LPS.