Male C57BL/6J (B6; H2Kb), BALB/c (H2Kd), B6.FVB-Tg(Itgax-DTR/EGFP)57Lan/J (CD11c-DTR), and B6.129P2-IL2tm1Hor/J (IL-2−/−) mice were purchased from The Jackson Laboratory (Bar Harbor, ME). BALB/c St2−/− mice were obtained from Dr. Andrew N.J. McKenzie and bred for experimental use25 (link). C57BL/6-Foxp3tm1Flv/J (Foxp3-IRES-mRFP; FIR) reporter mice26 (link) for breeding were graciously provided by Dr. Fadi Lakkis. All mice were housed in the specific pathogen-free facility at the University of Pittsburgh School of Medicine. Recombinant(r) mouse(m) IL-33 (BioLegend, San Diego, CA) was dissolved in PBS and injected intraperitoneally (0.5 μg/m/day(d); for 10 d). Control animals received PBS alone. Experiments were conducted under an Institutional Animal Care and Use Committee-approved protocol and in accordance with National Institutes of Health guidelines. Animals were fed a diet of Purina rodent chow (Ralston Purina, St. Louis, MO) and received food and water ad libitum.