Figure 4.

Histopathologic examination of iBALT formation. The experiment setup was the same as Figure 2 and histopathology was examined for day 1, 3 and 5 days after. The images of day 3 are shown (A-F) and semi-quantitation included all time points (G). (A-F) show the iBALT formation (light microscopy). Few iBALT was observed at 4 week group (A), while for the 6 month and 1 year groups, the number of iBALT (green arrow) especially those beside blood vessels or bronchials increased with age (C, E). No iBALT was observed in uninfected age control groups (B, D, F). Semi-quantification of iBALT formation (Figure G) indicated that iBALT formation, especially at three days after infection, increased with age. ***indicate P < 0.001 relative to the corresponding the different age group mice with 4 week age group mice. Mean ± SEM. (n = 3 mce in each group). Magnification, × 100 (A-F).