Figure 6: GM-CSF inhibits IL-21-mediated pro-IL-1β processing.

(a) cDCs were treated with 100 ng ml⁻¹ IL-21 and/or 20 ng ml⁻¹ GM-CSF for 4 h, and Il1b mRNA relative to Rpl7 assessed by RT–PCR. Data are from three experiments. Error bars are means±s.e.m. (b) cDCs were treated as in a for 24 h, and intracellular pro-IL-1β expression (top panel) and cell death (bottom panel) analysed by flow cytometry. Data are representative of three experiments. (c) cDCs were treated as in a for 24 h, and IL-1β protein determined. Data are from three experiments. (d) cDCs from Bcl2l11^+/+ and Bcl2l11^−/− mice were treated with IL-21 for 24 h, or LPS for 24 h with 5 mM ATP added in the final 1 h, and % apoptotic cells (Annexin V⁺ and/or 7-AAD⁺) assessed. NS, P=0.84. In c,d, error bars are means±s.e.m. (e) cDCs from Bcl2l11^+/+ and Bcl2l11^−/− were treated with IL-21 for 4 h, and Il1b mRNA relative to Rpl7 assessed by RT–PCR. Data are representative of three experiments; error bars are technical duplicates of the representative experiment; NS, P=0.14. (f) As in d, but IL-1β protein instead of apoptosis was determined. Data are from three experiments; error bars are means±s.e.m; NS, P=0.34. In c and f, IL-1β levels in the culture supernatant was determined by ELISA. Pro-IL-1β induced by IL-21 in the culture supernatant was minimal, based on a pro-IL-1β-specific ELISA. Statistical analysis was performed by Student’s t-test.