Increased myelopoiesis in response to infection is mediated by paracrine factors. (A) Schema of conditioned media experiments. Mice were irradiated (5 Gy) on day 0, followed by injection of 100 µL of CdM (dashed arrows) or media control on day 3. Mice were intranasally infected with P aeruginosa on day 7 and given a second dose of 100 µL CdM by tail vein 6 hours after infection. Mice were euthanized 9 days after irradiation for functional analysis. (B) Luciferase activity from 2 × 10⁶ lysed bone marrow cells harvested from mice given PBS, MSC-luciferase (MSC-luc), and CpG-MSC-luciferase (CpG-MSC-luc) after 5 Gy radiation. Data were analyzed by ANOVA, P = .0001. †Significant comparisons by Bonferroni’s multiple comparisons test, PBS vs MSC, P = .0009; *PBS vs CpG-MSC, P = .0002. (C) A total of 1000 c-kit⁺ cells isolated from the bone marrow of irradiated mice given CdM prepared from MSCs or CpG-MSCs or media control (n = 3 per group per experiment) and infected with pulmonary P aeruginosa were seeded into methylcellulose media in triplicate and total colony count quantified. Data were assessed by 2-way ANOVA; interaction P < .0001. †Significant comparisons by Bonferroni’s multiple comparisons test, PBS vs MSC, P < .0001; *PBS vs CpG-MSC, P < .0001; §CpG-MSC vs MSC, P < .0001. (D) Multiplex cytokine analysis of CdM from MSCs and CpG-MSCs (n = 3 per group). Data were analyzed by 2-way ANOVA; interaction P < .0001. ****Significant comparison by Bonferroni’s multiple comparisons test, PDGF-AA, MSC vs CpG-MSC, P < .0001. TUNEL staining of (E) left lung (n = 6 per group) and (F) kidney (n = 6 per group), standardized to total tissue area, relative to TUNEL staining in mice that received media control (fold change control). Data were assessed by Brown-Forsythe ANOVA, P = .013 (kidney), P = .006 (lungs). *Significant comparisons by Dunnett’s multiple comparisons test, control vs CpG-MSC, P = .023 (lung), P = .040 (kidney); †control vs MSC, P = .049 (lung).