IFN-γ up-regulates M-CSF and IL-6 production by IL-4 plus GM-CSF–stimulated monocytes.

(A,C) Monocytes in GM-CSF plus IL-4 were (■) or were not (▪) stimulated with 25 ng/mL IFN-γ at day 0 and M-CSF (A) and IL-6 (C) were quantified in the cell-free supernatants from day 1 to day 5. (B,D) Monocytes were cultured in GM-CSF (░) or GM-CSF plus IL-4 (■) in the absence or presence of 1 to 50 ng/mL IFN-γ added at day 0 and M-CSF (B) and IL-6 (D) were quantified in the 24-hour supernatants (day 1). As control, monocytes were cultured in medium without cytokine (dotted bars). (A-D) Results are expressed in micrograms per milliliter as means ± SDs of 4 experiments. (E) Monocytes in GM-CSF plus IL-4 were (■) or were not (▪) stimulated with 25 ng/mL IFN-γ. At days 1, 3, and 5, membrane CD115 expression was analyzed by FACS. At day 1, intracellular CD115 expression was analyzed after cell permeabilization. Results are expressed in MFI (after subtraction of the MFI obtained with the control mAb) as means ± SDs of 4 separate experiments. (F) Monocytes in GM-CSF plus IL-4 were not (▪) or were (■) stimulated with 25 ng/mL IFN-γ in the absence or presence of neutralizing anti–M-CSF plus anti–IL-6 mAbs or of isotype control mAbs. After 5 days, cells were stimulated with 20 ng/mL LPS and CD83 expression was analyzed by FACS. Results are expressed in MFI values as means ± SDs, n = 3.