ICAM-1 deficiency protects against virus-induced inflammation. Wild-type (+/+) and ICAM-1–null (–/–) mice were inoculated with SeV (5,000 EID50) and analyzed as follows. Lung sections were immunostained with anti–ICAM-1 (a) or anti-SeV Ab (b) and counterstained with hematoxylin on the indicated postinoculation days. Representative photomicrographs are shown for each genotype (four mice/genotype). Wild-type mice inoculated with PBS or SeV-UV revealed alveolar but not conducting airway epithelial staining for ICAM-1, and incubation of lung tissue with control nonimmune IgG resulted in no signal above background in either genotype (data not shown). Similarly, ICAM-1–null mice exhibited no detectable ICAM-1 staining above background (data not shown). Bar, 20 μm. (c) Bronchoalveolar lavage fluid was subjected to total and differential cell counts. Values represent mean ± SEM for four mice. For a–c, values obtained from +/+ and –/– cohorts inoculated with PBS or UV-inactivated SeV were no different from preinoculation values (data not shown). *Significant decrease compared with the wild-type cohort.