Figure 1. GM-CSF boosts LPS-induced IL-1 secretion.

(A) CD11b⁺ fraction of FLT3L derived DCs was stimulated 24 h with a wide range of different LPS concentrations (0.001–10 µg/ml) in absence (white circles) or presence of 5 ng/ml GM-CSF (black circles). 5 mM ATP was added as a danger signal. Released IL-1β, IL-1α, TNF-α and IL-6 were measured in the culture supernatants by standard ELISA and each value represents the mean of triplicates +/− SD. (B) CD11b⁺ fraction of FLT3L generated DCs was primed for 24 h with 100 ng/ml LPS with (back bars) or without (white bars) 5 ng/ml GM-CSF and stimulated with different danger signals (5 mM ATP, 1 µM nigericin, 100 µg/ml MSU, 200 µg/ml Alu). Each bar represents the mean of triplicates +/− SD. (C) CD11b⁺ fraction of FLT3L generated DCs was primed with TLR agonists (100 ng/ml LPS and Pam₃CSK₄), Dectin agonist, Curdlan (100 µg/ml) and pro-inflammatory cytokine TNF-α (100 ng/ml) in absence (white bars) or presence (back bars) of 5 ng/ml GM-CSF and stimulated subsequently with ATP. Each bar represents the mean of triplicates +/− SD. (D) GM-CSF derived BM DCs, M-CSF-derived BM MØ as well as L929-derived BM MØ were compared to the CD11b⁺ fraction of FLT3L-derived DCs for their capacity to secrete IL-1β upon 24 h LPS stimulation (100 ng/ml) in absence or in presence of GM-CSF (5 ng/ml). ATP was added as danger signal. Both, WT (black bars) and GM-CSF R−/− cells (white bars) were tested. Each bar represents the mean of triplicates +/− SD. All results are representative of at least two independent experiments.