Diminished T-bet expression in NP-specific CD4 ⁺ T _RM in the lung can be driven by IL-33 and is dependent on ST2 signaling in CD4 ⁺ T cells. (A) Schematic of the experimental timeline for data in B–C. (B) Representative flow cytometry plots of CD4⁺ T cells isolated from the lung at experimental day 27. (C) Summary data of the percentage of T-bet⁺ NP-specific cells, the geometric mean fluorescence intensity of T-bet in NP-specific cells, and the percentage of ST2⁺ NP-specific cells as represented in B. Data are pooled from six mice per group from two independent experiments. (D) Schematic of the experimental timeline for data in E and F. (E) Representative flow cytometry plots of CD4⁺ T cells isolated from the lung on experimental day 27. Red box gate and numbers define the T-bet⁺ population and associated frequency, respectively. (F) Summary data of the percentage of T-bet⁺ NP-specific cells, the geometric mean fluorescence intensity of T-bet in NP-specific cells, and the percentage of ST2⁺ NP-specific cells as represented in E. Data are pooled from eight to nine mice per group from three independent experiments. (G) Schematic of the experimental timeline for data in H–J. (H) Representative flow cytometry plots and summary data of ST2 expression by CD4⁺ and CD4⁻ cells isolated from the lung at experimental day 48. Plots are pregated on CD45.2⁺, B220⁻, CD8⁻, CD19⁻, F4/80⁻, CD11b⁻, CD11c⁻, TCR γΔ⁻, and NKG2d⁻ cells. Data are pooled from 10–11 mice per group from three independent experiments. (I) Representative flow cytometry plots of CD4⁺ T cells isolated from the lung at experimental day 48. (J) Summary data of the percentage of T-bet⁺ NP-specific cells as represented in I. Data are pooled from 10–11 mice per group from three independent experiments. *, P < 0.05; **, P < 0.01; ****, P < 0.0001. Graphs show mean ± SD and data were analyzed by unpaired t test. pfu, plaque-forming units. IAV, influenza A virus. o.p., oropharyngeal. gMFI, geometric mean fluorescence intensity.