Concentrations of IFN-γ (A) and TNF-α (B) in lungs of mice infected with r-06 (
) and r-06/NA2 (
) strains. Concentrations of cytokines were determined via ELISA in lung supernatants taken from different days after infection. The results are expressed in terms of pg/g. *P < 0.05 indicates a significant difference for r-06 group compared with r-06/NA2 group. #
P < 0.05, ##
P < 0.01, or ###
P < 0.005 indicates a significant difference between the infected groups and the PBS control group.