FIG. 3.

Active TGF-β level in infected mice. Mice were infected intranasally with Italy/97 (10^5.8 ELD₅₀), Scot/59 (10^6.0 ELD₅₀), Eng/91 (10^6.2 ELD₅₀), Q20/95 (10^6.0 ELD₅₀), HK728 (10^5.2 ELD₅₀), HK156 (10^5.8 ELD₅₀), HK220 (10^6.2 ELD₅₀), or PBS (sham-inoculated controls). Blood was collected from mice at 8, 48, and 96 h p.i., and serum was analyzed for TGF-β activity by the NRK colony-forming soft agar assay. Three mice per group were analyzed, and the results represent the means ± standard deviations of triplicate determinations from the pooled sera.