Figure 2.

Immunohistochemical staining of H1N1 antigen in mice lung. The experiment set up is the same as in Figure 1 (inoculation at 10LD₅₀ dose, n = 3 for each age group at each time point) except that there was a non-treated negative control group for each age. The tissues were stained with a polyclonal anti-HA antibody. No antigen was detected in the negative control group (A-C). At 1 day after inoculation, almost all the bronchi and bronchiolar epithelium cells in the 4-week age-group were positively stained (D), while less than half of the bronchi and bronchiolar epithelium cells were stained brown in the 6-month and 1-year age group (E,F). At 3 days and 5 days after inoculation, most positive stained bronchi and bronchiolar epithelium cells death and collapsed into bronchi and bronchiolar lumina (G-L). Magnification, × 200.