Secretagogue effect on BLyS by proinflammatory mediators. Neutrophils were incubated with or without G-CSF or IFN-γ for 20 hours before the addition of CXCL8, C5a, fMLP, IC, or TNF-α. Cell-free supernatants and the corresponding cell pellets were harvested after 4 hours and were analyzed for the content of antigenic BLyS. Percentages of secreted BLyS were calculated from the total BLyS levels. Data report the mean ± SEM of the percentages of BLyS release under the various conditions (calculated from 6 and 3 experiments for G-CSF– and IFN-γ–treated neutrophils, respectively).