Induction of interleukin (IL)-6, IL-8, and B cell-activating factor (BAFF) synthesis by microparticles (MPs) isolated from lipopolysaccharide (LPS)-activated THP-1 cells. THP-1 cells were treated with LPS (15 μg/mL) for 18 hours, and MPs were isolated as described in Materials and methods. Rheumatoid arthritis (RA) FLSs were stimulated with 40 nM phosphatidylserine equivalents of MPs isolated either from THP-1 cells (MP THP-1) or from LPS-activated THP-1 cells (MP THP-1 LPS). Culture supernatants were harvested 24 hours after stimulation for IL-6 (a) and IL-8 (b) determination and 72 hours after stimulation for BAFF secretion (c) by enzyme-linked immunosorbent assay. LPS (IL-6 and IL-8) and interferon-gamma (IFN-γ) (BAFF) were used as positive controls. Data are expressed as the mean of triplicate samples ± standard deviation and are representative of three independent experiments. C, control medium; TMP, control Hanks' balanced saline solution.