FIG. 3.

Kinetics of cytokine production by THP-1 cells in response to HBb (10⁷/ml) (heat-killed spirochetes of the JD1 strain), L-OspA (1 μg/ml), and LPS (1 μg/ml). Vitamin D₃-treated THP-1 cells (10⁶/ml) were incubated with stimulants, and cell-free supernatants were collected at 2, 8, 16, 24, 48, 72, 96, 120, 144, and 168 h after addition of stimulants to THP-1. TNF-α, IL-1β, IL-6, and IL-10 in 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. All tested cytokines were below detection limits in the absence of stimulants. Data are representative of those from three separate experiments.