IL-25 elicits ILC2 and MPP^type2 cells independent of IL-33 signaling. (a–d) C57BL/6 WT mice and C57BL/6 Il33^−/− mice (Taconic) were treated i.p. with PBS (control) or 0.3 µg of recombinant IL-25 daily for 7 d. MLNs were harvested at day 7, and the frequency and total cell numbers of ILC2 and MPP^type2 cells were assessed by flow cytometry. (a and c) Frequency of ILC2 in control or IL-25–treated WT (a) or Il33^−/− mice (c). (b and d) Total cell numbers of ILC2 in control or IL-25–treated WT (b) or Il33^−/− mice (d). (e and g) Frequency of MPP^type2 cells in control or IL-25–treated WT (e) or Il33^−/− mice (g). (f and h) Total cell numbers of MPP^type2 cells in control or IL-25–treated WT (f) or Il33^−/− mice (h). Data in a–h are representative of two independent experiments (control, n = 4; IL-25–treated WT, n = 6; IL-25–treated Il33^−/−, n = 6). (i–l) BALB/c WT mice (The Jackson Laboratory) were treated with PBS (control) or 0.3 µg of recombinant IL-25 plus isotype (IgG) or anti-T1/ST2 mAbs. MLNs were harvested at day 7, and the frequency and total cell numbers of ILC2 and MPP^type2 cells were assessed by flow cytometry. Frequency and total numbers of T1/ST2^pos IL-7Rα^pos ILC2 (i and j) and T1/ST2^neg IL-7Rα^neg c-kit^pos MPP^type2 cells (k and l). Plots are gated on live, Lin^neg (CD4, CD8α, CD11b, CD11c, and CD19) cells. Data in i–l are representative of two independent experiments (control, n = 6; IL-25 treated, n = 9; anti-T1/ST2 IL-25 treated, n = 9). Error bars indicate SEM.