pDC depletion predisposes toward severe PVM-induced bronchiolitis and subsequent asthma in neonatal but not adult mice. (a) Study design. 1-wk-old (neo) or 6-wk-old (adult) pDC^Δ and WT mice were treated with DT (i.p. route, 15 ng) at −1, 1, 3, and 5 dpi, inoculated with PVM or vehicle at 0 dpi, and killed at 7 and 10 dpi. (b and c) pDC (CD11b⁻ B220⁺ CD11c⁺ Siglec-H⁺ CD45RA⁺) number in lung (b) and MLNs (c). (d) IFN-α, IFN-λ, and IL-12p40 protein expression in BALF. (e) Representative micrograph (x1000 magnification) of PVM immunoreactivity in the airway epithelium, and quantification of PVM positive AECs. Bars, 50 µm. (f) Quantification of AEC sloughing. (g) Neutrophil and eosinophil numbers in BAL. (h) Proinflammatory cytokine production in lung tissue. (i) Type-2 cytokine production in BALF. (j) Representative flow cytometry plots and number of type 2 ILCs in lung. Quadrants display percentage of parent population. (k) Representative flow cytometry plots and numbers of IL-13 (dsRed) and IL-4 (AmCyan) expressing type 2 ILCs, CD4⁺ and CD8⁺ T cells in lungs of WT/4C13R and pDC^Δ/4C13R mice at 10 dpi. Data are representative of n = 2 experiments with 6–8 mice per group and presented as box-and-whisker plots showing quartiles (boxes) and range (whiskers). Data were analyzed using one-way ANOVA with Tukey’s post hoc test; *, P < 0.05; **, P < 0.01; ***, P < 0.001.