Injection of DT in PMN^DTR mice induces marked depletion of neutrophils and enhances susceptibility to LPS-induced endotoxemia. (A) GFP expression (mean fluorescence intensity [MFI]) among leukocytes in the blood, BM, spleen, and peritoneal lavage fluid of MRP8-Cre/iresGFP⁺ mice and MRP8-Cre/iresGFP⁻ littermate controls. Results in A are pooled from three independent experiments, each column representing data from one mouse. (B–D) Numbers of blood (B), spleen (C), and BM (D) neutrophils 24 h after i.p. injection of 500 ng DT into PMN^DTR mice and PMN^WT littermate control mice. Results in B–D show values from individual mice; bars indicate means ± SEM pooled from three (C and D; total n = 7–8/group) or four (B; total n = 15–16/group) independent experiments. (E and F) Changes in body temperature (Δ°C [mean ± SEM]; E) and survival (percentage of live animals; F) after LPS injection in DT-treated PMN^DTR and PMN^WT mice. Data in E and F are pooled from three independent experiments (total n = 11/group); arrows indicate days of i.p. injection of DT. (G) Percentage of blood neutrophils before (time 0) and 3, 6, and 20 h after LPS injection in DT-treated PMN^DTR mice and PMN^WT controls. Data show values from individual mice; bars indicate means ± SEM pooled from three independent experiments (n = 6–10/group). (H–L) Levels of TNF-α (H), IL-6 (I), IL-10 (J), IFN-γ (K), and MCP-1 (L) in the plasma of DT-treated PMN^DTR mice and PMN^WT littermate controls before (time 0) and 6 h after LPS injection (n = 6–16/group). Results in H–L are means ± SEM pooled from three independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001 versus PMN^WT group and ^#, P < 0.05; ^##, P < 0.01; ^###, P < 0.001 versus same group at time 0 by Mann–Whitney U test (B–D and G–L) or Mantel–Cox log-rank test (E and F).