CpG ODN 10103 administered intranasally 48 h prior to infection differently effects B. pseudomallei 1026b and F. tularensis Schu S4 pathogenesis in aerosol-challenged mice. At 6 days post infection, mice challenged with B. pseudomallei developed bronchopneumonia and pulmonary abscesses (A: arrowheads) and areas of liver necrosis (B: arrows). By contrast, B. pseudomallei-infected mice pretreated with CpG ODN developed only mild interstitial pneumonia (C) and lymphoplasmacytic hepatitis (D: arrows). F. tularensis-challenged mice exhibited bronchopneumonia and pulmonary abscesses (E, G: arrows) and areas of liver necrosis (F, H: arrows) 6 days after infection regardless of whether or not they received CpG ODN. Cytokine levels in the livers and lungs of saline (red circles)- and CpG ODN (blue squares)-treated mice differed significantly for mice infected with B. pseudomallei but not F. tularensis. Mean cytokine levels for tissues obtained from mice 1, 3, and 6 days after infection are rendered as colored bars. Asterisks indicate statistically significant differences (p < 0.05) between saline- and CpG ODN-treated groups on day 6. Parenthetical values accompanying cytokine labels indicate numbers of independent data points obtained for saline- and CpG ODN-treated mice. Cytokine concentrations below 1 pg/ml fall below the x-axis and are not shown on the graphs. T-tests were used to support qualitative analysis of CBA-generated cytokine data.