Neutrophil recruitment into the infected mucosa is decreased in absence of IL-18 but neutrophil depletion does not seem to be a main driver during the initiation of mucosal inflammation.

(a) Il18^-/- mice and littermate controls were Sm-pretreated, infected orally with 5x10⁷ CFU S.Tm for 12h (n = 3–4 per group). RNA-Seq was performed on RNA extracted from complete cecum tissue. RNA-Seq analysis: The Volcano plot shows the induction (log₂ fold change) versus the -log₁₀ p-value for all chemokines. Chemokines able to induce neutrophil recruitment are highlighted in green. (b) C57BL/6 WT mice and Il18^-/- mice and littermates were Sm-pretreated and either uninfected (WT) or infected orally with 5x10⁷ CFU S.Tm for 12h (n = 4–5 per group). Cxcl1 and Cxcl2 mRNA levels in whole cecum tissue were measured by RT-qPCR. Results are presented relative to the expression of Actb. (c and d) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x10⁷ CFU S.Tm (n = 6 per group). Single live cells were gated on CD45⁺CD3^-CD19^-CD11b⁺ cells. (c) Representative dot plots and (d) quantification of Ly-6G⁺ cells. (e and f) Flow cytometric analysis of isolated cecal LP cells from Il18^-/- mice and littermates, Sm-pretreated and orally infected with 5x10⁷ CFU S.Tm for 12h (n = 8 per group). Single live cells were gated on CD45⁺CD3^-CD19^-CD11b⁺ cells. (e) Representative dot plots and (f) quantification of Ly-6G⁺ cells. (g and h) C57BL/6 WT mice were injected intraperitoneally with anti-G-CSF (0.4mg/kg; two consecutive days) and anti-Ly-6G (6mg/kg; two days prior to infection) or PBS. Mice were Sm-pretreated and infected orally with 5x10⁷ CFU S.Tm for 12h (n = 6 per group). (g) Pathological score and (h) representative HE-stained cryosection. Data represent the mean ± SD and statistical analysis was performed using the Mann-Whitney-U test (ns = not significant, *: p<0.05; **: p<0.01).