Time course of PlGF-mediated secretion of chemokines from THP-1 cells. THP-1 cells (1 × 10⁶/mL) were treated with PlGF (250 ng/mL) for time periods of 1 to 24 hours. Cell-free supernatant was collected, and 100 μL from the total 1 mL supernatant was used for determining levels of (A) MIP-1β, (B) MCP-1, and (C) IL-8 using the DuoSet ELISA from R&D Systems. Data are means ± SD of n = 3, each experiment run in duplicate.