Comparison of club cell, AT1, and AT2 coverage in oseltamivir-treated and untreated aged mice following influenza infection. A-C. Club cell coverage index (A), AT1 coverage index (B), and AT2 density (number per mm2 tissue area) (C) in the aged mice with (solid column) and without (open column) oseltamivir treatment following influenza infection. Five oseltamivir-treated and 5 untreated aged mice were used for each time-point. All error bars represent standard errors. *p < 0.05, **p < 0.01 by Student t-test. D-O. Representative immunofluorescence staining of lung sections for SCGB1A1 (green) and pro-SPC (red) in D-I (DAPI stain is not shown), and PDPN (red) and DAPI (blue) in J-O at 6, 12 and 21 dpi. The arrows point to loss of SCGB1A1-expressing club cells; the insert in D shows a magnified view of a bronchiole with club cell loss; in D-I the dotted lines circle the regions with loss of pro-SPC-expressing AT2s; in J-O the dotted lines circle the regions with loss of PDPN-expressing AT1s. Scale bar: 500 μm.