Effect of IL-15 and IL-2 towards the production of IL-8 in human neutrophils. (A) Cells (106/300 μL) were cultured at 37°C in the presence or absence (–) of 250 ng/mL IL-15 (ie, 20 nmol/L) or 1 μg/mL LPS for the indicated times (in hours). Culture supernatants were collected, and their IL-8 concentration was determined using a specific ELISA. Results are expressed as mean ± standard error of mean (s.e.m.) of duplicate determinations for each experimental condition. Depicted in this panel is a representative experiment; the ability of 20 nmol/L IL-15 to induce IL-8 release was observed in seven independent experiments (P = .002 versus unstimulated cells). (B) Neutrophils (106/300 μL) were cultured for 9 hours at 37°C in the presence or absence of increasing concentrations of either IL-15 (closed squares) or IL-2 (open squares). The IL-8 content of the resulting culture supernatants was then determined by ELISA. Values are the mean ± s.e.m. of duplicate determinations for each experimental condition. This experiment is representative of at least three. (C) Neutrophils (106/300 μL) were cultured for 20 minutes at 37°C in the presence of 10 μg/mL cycloheximide (CX) or its diluent (DMSO), before stimulation with 250 ng/mL IL-15 (ie, 20 nmol/L), 103 U/mL IL-2 (∼5 nmol/L), or diluent control (ctrl), for 8 hours at 37°C. Cell-free culture supernatants and the corresponding cell pellets were collected, and their respective IL-8 concentrations were determined by ELISA. Values are the mean ± s.e.m. of averaged duplicate determinations from three independent experiments. Open bars, IL-8 release; shaded bars, total IL-8 production (ie, released + cell-associated). *, P < .04 relative to control cells, using Student’s t-test for paired data; CX treatment also yielded significantly lower (P < .05) values relative to the matched controls for all conditions tested.
