FIG. 1.

Dose-response analysis of stimulants required to induce optimal levels of TNF-α, IL-1β, IL-6, and IL-10 production. Vitamin D₃-treated THP-1 cells (10⁶/ml) were incubated for 48 h with supplemented medium (RPMI), various concentrations of HBb (heat-killed spirochetes of the JD1 strain), L-OspA, U-OspA, and LPS. TNF-α, IL-1β, IL-6, and IL-10 in the cell-free supernatants were quantified by Ab capture ELISA. The lower limit of detection of the ELISA was 15 pg/ml. Each bar represents the mean ± standard deviation for duplicate cultures. Data are representative of those from two separate experiments.