CXCL8, C5a, fMLP, insoluble IC, and TNF-α induce the secretion of BLyS from the intracellular pool accumulated in G-CSF–treated neutrophils. Neutrophils (2 × 10⁶/400 μL) were incubated with or without G-CSF for 20 hours before the addition of CXCL8, C5a, fMLP, IC, or TNF-α. After an additional 4 hours, cell-free supernatants and the corresponding cell pellets were harvested for determination of antigenic BLyS and IL-1ra. Mean ± SEM of the total production (depicted as cell-associated and released) of BLyS (A), and IL-1ra (B), from 6 and 3 donors, respectively.