FIG. 4.

Representative images of the histopathologic effect of IL-1R deficiency in mice infected with HK/486 virus. B6/129 and IL-1R-deficient mice were infected with 1,000 MID₅₀ of HK/483 or HK/486 virus. Tissues were removed on the indicated day p.i. and routinely processed for histopathologic and immunohistochemical analyses. (A and B) Representative H&E images showing similar histologic features in lungs of naïve B6/129 (A) and IL-1R-deficient (B) mice. (C to F) Representative H&E images showing inflammatory infiltrates in the lungs of B6/129 (C and E) and IL-1R-deficient (D and F) mice on day 6 and 9 p.i. with HK/486 virus. Immunostaining of influenza virus antigen was observed in bronchiolar epithelial cells of IL-1R-deficient mice on day 9 p.i. (F, inset), whereas B6/129 mice showed only scattered antigen staining in alveolar cells (E, inset). Bars, 100 μm.