(A) Schematic describing intratracheal treatment of hIL33^CrimBAC mice with 100 ng of recombinant IL-33 (rIL33). Crimson fluorescence was measured in lung stromal cells 24 hours later. (B) Crimson expression in CD45^– cells from the lungs of hIL33^CrimBAC mice treated with PBS or rIL33, expressed as percentage of cells positive for Crimson. (C) Crimson⁺ cells in the lungs of hIL33^CrimBAC mice treated with PBS or rIL33, quantified as total backcalculated number of Crimson⁺ cells. (D) Schematic describing i.t. treatment of ST2 KO x hIL33^CrimBAC mice with PBS or 100 ng rIL33. (E) Crimson expression in CD45^– cells from the lungs of ST2 KO x hIL33^CrimBAC mice treated as in D. (F) Crimson⁺ cells in the lungs of ST2 KO x hIL33^CrimBAC mice treated with PBS or rIL33, quantified as total backcalculated number of Crimson⁺ cells. (G) Schematic describing i.t. treatment of hIL33^CrimBAC5KbDel mice with PBS or 100 ng rIL33. (H) Crimson expression in CD45^– cells from the lungs of hIL33^CrimBAC5KbDel mice treated as in G. (I) Crimson⁺ cells in the lungs of hIL33^CrimBAC5KbDel mice treated with PBS or rIL33, quantified as total backcalculated number of Crimson⁺ cells. (J) Crimson transcript levels in total lung digests from hIL33^CrimBAC mice treated intratracheally with PBS or rIL33 as in A. (K) Quantification of IL33 transcripts in HUVECs, hiLECs, and HMVECs 24 hours after treatment with the indicated dose of rIL33. Data in A–I are from 2 independent experiments with n ≥ 3 samples per treatment. Data in J are from a single representative experiment. Data for each cell line in K are from a single experiment with n ≥ 3 technical replicates. Data in B–F and K are represented as mean ± first and third quartile; data in J depict all individual values with a dotted line at the mean. *P < 0.05; **P < 0.01 by unpaired t test.