Stim1^−/−chimeras have major impairment in host defense to S aureus pneumonia and L monocytogenes septicemia. WT or stim1^−/− chimeras were inoculated with S aureus (Newman strain) via direct tracheal intubation. At 24 hours, the mice were euthanized and the lungs were isolated. Representative gross specimens are shown in (A). (B) The left lobe of the lung was homogenized, and serial dilutions were plated for assessment of bacterial colony-forming assays (shown as CFU/organ). Data shown are pooled from 2 independent experiments. n = 10 mice per group. **P < .03. The right lobes were digested with collagenase and cells were collected for total cell count (C) and analysis via flow cytometry (D). Neutrophils were identified by double-staining for CD11b and Ly6G. (E) WT or stim1^−/− chimeras were infected by intravenous injection of L monocytogenes into the retroorbital sinus. Liver or spleens were isolated 2 days postinfection. Representative organs are shown. (F) Total tissue homogenates were prepared in LB medium, and samples were plated on LB plates for Listeria colony-forming assays (shown as CFU/mL). Results are pooled from 2 separate experiments. n = 11 mice per group. ***P < .001. (G) Liver samples from WT or stim1^−/− chimeric mice obtained 2 days following Listeria infection were stained with trichrome to visualize leukocyte abscesses (shown by arrows). Microscopy sections are at ×10 magnification and are representative of 3 different animals in 2 separate experiments.