Allergic airway inflammation induced by the fungal aeroallergen A. alternata promotes increased serum IL-33 and ILC2P egress from the bone marrow. (A) Adult WT mice were treated for four consecutive days with an intranasal challenge of A. alternata extract or PBS vehicle and killed 24 h after the final treatment. (B) Representative gating for ILC2Ps in the bone marrow. (C) The total number of viable bone marrow cells. (D) The total number of FSC-A^lo SSC-A^lo cells in the bone marrow. (E) ILC2P frequency among live bone marrow cells. (F) The total number of ILC2Ps in the bone marrow. (G) The concentration of IL-33 in the serum as measured by ELISA. (H) The total number of FSC-A^lo SSC-A^lo cells. (I) ILC2Ps in WT and St2^−/− mice treated for four consecutive days with Alternaria extract. For H and I, PBS-treated WT and St2^−/− mice were normalized to 100%, and Alternaria extract–treated mice are displayed as a percentage of PBS-treated within each genotype (WT and St2^−/−). Data are combined from two (H and I, n = 7) or three independent experiments (C–G, n = 13–15) or representative of three independent experiments (B) and displayed as the mean ± SEM. *, P < 0.05; ***, P < 0.001 by unpaired t test (C–G) or one-way ANOVA with Bonferroni posttest (H and I); n.s., not significant. Dashed line in G indicates limit of detection of the assay. Values within flow plots indicate percentage of the parent population.