Neutrophil infiltration in lymphatic organs. (A) Neutrophil counts in spleen, mLN, iLN, and aLN at different points after TBI were analyzed by flow cytometry. Fold change of absolute numbers with regard to untreated mice (day 0) is presented (n = 6 for each point and organ from 2 independent experiments). (B) Giemsa-Wright staining of mLN-derived CD45⁺CD11b⁺Ly6G⁺ neutrophils after FACS sorting and cytospin. (C) Correlation of neutrophil frequency in mLN and ileum from WT or solvent control-treated mice (n = 57). (D) Bacterial load in mLN of untreated C57BL/6 and 48 hours after TBI were analyzed by quantitative reverse transcription-polymerase chain reaction. 16S rDNA content was normalized to genomic DNA (glyceraldehyde-3-phosphate dehydrogenase). (E) Fold change of neutrophil numbers on day 2 after TBI normalized day o d0 (no TBI) in C57BL/6 mice with and without gut decontamination is shown (Control treatment, n = 10; gut decontamination, n = 6 each point and organ from 2-3 independent experiments). (F) C57BL/6 mice were treated daily by subcutaneous injection of aztreonam (75 mg/kg/d) or solvent control from day −7 until day +1 and underwent TBI on day 0. Fold change of neutrophil numbers on day 2 post TBI normalized to mean of solvent controls is shown (n = 11 pooled from 2 independent experiments). (G) BALB/c mice were treated daily by subcutaneous injection of aztreonam (75mg/kg/day) or solvent control from day −7 until day +1 and received allo-HCT (C57BL/6 into BALB/c; 5 × 10⁶ BM cells + 0.3 × 10⁶ CD4⁺/CD8⁺ T cells) on day 0, and survival was monitored (n = 20 for each group pooled from 2 independent experiments). (H) C57BL/6 mice received 20 mg/kg doxorubicin on day 0 or were left untreated. The mLN were analyzed on day 3 by flow cytometry to assess neutrophils counts (CD45⁺CD11b⁺Ly6G⁺). Fold change of neutrophil numbers normalized to the mean of untreated samples is shown (n = 10 for each group pooled from 2 independent experiments).