BM ILC2s become activated and produce GM-CSF after BM stress. (A) Representative flow cytometry plots of BM cells to identify Lin⁻CD25⁺IL-7Rα⁺IL-33R⁺ ILC2s. (B) Percentage of ILC2s among BMMNCs; n = 4, representative of two independent experiments. (C) Number of ILC2s in femurs and tibias; n = 4, representative of two independent experiments. (D) Mean fluorescence intensity (MFI) of markers in ILC2 population; n = 4, representative of two independent experiments. (E) qRT-PCR analyses for the expression of Csf2 in B cells, T cells, neutrophils, monocytes, and ILC2s; n = 3–6, representative of two independent experiments. Bars indicate expression level relative to that in total BM cells at day 0. (F) Intracellular GM-CSF levels in Lin⁻IL-33R⁺ population. The tinted lines show the background levels. Results shown are representative of two independent experiments. For the 5-FU–treated mice groups, mice were injected intravenously with 200 mg/kg 5-FU 2 d before being euthanized (A–F). In the bar charts, results are shown as mean ± SEM, and each dot represents an individual mouse. Statistical significance was determined between the control (Ctrl) and 5-FU–treated mice by unpaired Student’s t test (B–E). ND, not detectable.