(A–C) Cellular response to infection in bronchoalveolar lavage fluid (BALF) determined by flow cytometry — alveolar macrophages (Alv Macs) (CD45⁺SiglecF⁺CDll11b^lo-mid), granulocytic myeloid-derived suppressor cells/neutrophils (G-MDSCs/NEUTs) (CD45⁺CD11b⁺MHCII^loLy6C^hiLy6G^hi), and monocytic myeloid-derived suppressor cells (M-MDSCs) (CD45⁺CD11b⁺MHCII^loLy6C^hiLy6G^lo). Horizontal lines represent median values and each data point represents an individual mouse. All data were compiled from 2 independent experiments, n = 6. *P < 0.05, compared with uninfected (un) control, Kruskal-Wallis test, 1-way ANOVA, Dunn’s correction for multiple comparisons. (D) Changes in surface markers associated with M-MDSCs and G-MDSCs/NEUTs determined by geometric mean fluorescence intensity (MFI), n = 6. For box-and-whiskers plots, horizontal lines indicate the median, boxes indicate 25th to 75th percentiles, and whiskers indicate minimum and maximum values of the data set. (E) Levels of TNF measured by ELISA from supernatants from immortalized bone marrow–derived macrophages (BMDMs) (WT, Tlr4^–/–, or Trif^–/–) incubated with KP35 or E. coli LPS (10 μg/ml) as a positive control for 4 hours. Representative graph of 2 independent experiments, n = 3 per condition. (F) Cytokine and chemokine production by Ly6C⁺ cells isolated from WT mice following exposure to KP35 (1 × 10⁸ to 2 × 10⁸ CFU) or E. coli LPS (50 μg), measured by qRT-PCR compared with PBS control. n = 7–9. For B–D, columns represent mean values ± SEM, horizontal bars represent P < 0.05 by 1- or 2-way ANOVA followed by Bonferroni’s or Dunn’s correction for multiple comparisons.