pDC depletion diminishes the expansion of Nrp-1⁺ T reg cells and IL-10 production in the lung during early-life PVM infection. (a) FoxP3⁺ cells enumerated in lung tissue sections. (b) Histogram of Nrp-1 expression on T reg cells (gated on CD4⁺ CD3ε⁺ CD25⁺ CD25⁺ Foxp3⁺; top) and number of Nrp-1⁺ T reg cells in lung (bottom). (c) Number of Nrp-1⁺ T reg cells in MLN. (d) Representative flow cytometry plots of BrdU expression by Nrp1⁺ T reg cells in MLN. (e and f) Proliferating BrdU/Nrp-1⁺ T reg cells in MLN. Kinetics of pDC number in lung (e) and MLN (f). (g) MHCII expression on pDCs. (h) IL-10 protein expression in lung (left) and IL-10-GFP⁺ cells in lung (middle) and MLN (right). (i) Immune-suppressive expression on Nrp-1⁺ T reg cells in lung. Data are representative of n = 2 experiments with four to six neonates in each group and are presented as mean ± SEM (a–c and f) or as box-and-whisker plots showing quartiles (boxes) and range (whiskers; d, f, and g). Data were analyzed by one-way ANOVA with Tukey post hoc test (a–f and h) or Mann–Whitney U test (g, h [right], and i); *, P < 0.05; **, P < 0.01; ***, P < 0.001 compared with the WT control group.