NP-specific CD4 ⁺ T _RM in the lung express IL-18Ra. (A) Schematic of the experimental timeline for data in B and 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 IL-18Ra⁺ NP-specific cells as represented in B. Data are pooled from six mice per group from two independent experiments. *, P < 0.05. Graphs show mean ± SD and data were analyzed by unpaired t test. pfu, plaque-forming units. IAV, influenza A virus. o.p., oropharyngeal.