Specific effect of SCH 14988 on G-CSF production by human PBMNCs. (A) Cells were cultured with PHA in the presence of varying concentrations of SCH 14988 or vehicle (0.1% DMSO). Data, expressed as percent of control, is normalized to the PHA plus vehicle (0 μmol/L SCH 14988) value, which was arbitrarily set at 100%. Each data point represents 4 to 12 donors; standard error was less than 20%. Absolute levels of each cytokine (in pg/mL) in the PHA plus vehicle group were IL-1α, 412 ± 113; IL-1β, 1,662 ± 304; IL-2, 781 ± 169; IL-3, 257 ± 36; IL-6, 10,367 ± 2,268; IL-8, 4,600 ± 246; TNFα, 2,225 ± 297; TNFβ, 1,890 ± 604; GM-CSF, 758 ± 205; and G-CSF, 3,018 ± 231. In the presence of PHA plus 25 μmol/L SCH 14988, G-CSF levels were increased to 14,185 ± 509 pg/mL. This increase in G-CSF levels was statistically significant relative to the PHA plus vehicle group, as determined by the Students' t-test (P < .01). For each cytokine, production was always less than 65 pg/mL in unstimulated cultures. (B) Steady-state G-CSF mRNA levels in PBMNCs cultured with vehicle (lane 2), PHA (lane 3), SCH 14988 alone at 25 μmol/L (lane 4), or PHA plus SCH 14988 (lane 5) for 24 hours. One kilobase ladder is shown in lane 1. Ethidium bromide-stained 1% agarose/Tris-acetate-EDTA gels are shown.