Figure 9. IL-33, ST2, MyD88 and STAT1 orchestrate activation and maturation of DCs.

Purified splenic CD11c⁺ cells from B16-SIY-bearing mice (A) or tumor-free mice (B) were incubated with the indicated reagents for 48 hours, and frequency of CD40, CD80, CD86, or MHC-II in Gr-1⁻CD11c⁺ cells was assessed by flow cytometry. (B) IL-33 induced maturation of naïve DCs is also ST2 dependent. (C) rIL-33-treated DCs promote antigen-specific CD8⁺ T cell proliferation. CD11c⁺ cells were treated with the indicated reagents for 48 hours as in (B), then pulsed with gp100 peptides for 2 hours. After pulsing they were cocultured with eFluro450-labeled naïve Pmel CD8⁺ T cells for 3 days and proliferation was measured by eFluro450 dilution. (D) rIL-33-induced STAT1 activation is ST2 and MyD88 dependent. Purified splenic WT or MyD88^−/− CD11c⁺ cells were incubated with indicated reagents and then stained intracellularly for phosphorylated STAT1 by flow cytometry. (E) rIL-33-induced STAT1 phosphorylation is DC intrinsic. Purified CD3⁻CD11c⁺ WT and eFluro450-labeled MyD88^−/− DCs were mixed at a 1:1 ratio and treated with/without rIL-33. The next day cells were analyzed for STAT1 phosphorylation by flow cytometry. WT DCs were gated as e450⁻, while MyD88^−/− DCs were CD3⁻CD11c⁺ e450⁺. *; p<0.05, **; p<0.01, ***; p<0.001. Data (mean ± SEM) are representative of 3 independent experiments.