FIG. 8.

Rapid neutrophil recruitment requires caspase-1 expression in a radiosensitive cell compartment. Bone marrow chimeras were constructed using irradiated 3- to 4-week-old caspase-1^−/− (Ly5.1) and C57BL/6 (Ly5.2) mice as donors or recipients. Chimeric animals were infected with 5 × 10⁴ CFU of ΔUT bacteria intranasally and then sacrificed at 4 h.p.i. Chimerism was confirmed by FACS analysis of splenic lymphocytes. Each point represents the value for an individual animal. (A) Bacterial recovery from lung tissue is expressed as the ratio of output CFU to input inoculum; lines indicate geometric means (P = 0.09, Kruskal-Wallis test). (B to D) Total cells (B), neutrophils (C), and macrophages (D) present in BAL fluid are shown; lines indicate median values, which differ significantly by Kruskal-Wallis test for total cells (P = 0.0006) and neutrophils (P = 0.0002). P values for all pairwise comparisons were calculated with Dunn's multiple-comparison test and are indicated whenever the P value is <0.05 (*, P < 0.05; **, P < 0.01; ***, P < 0.001). (E) Percentages of neutrophils and macrophages in BAL fluid (means ± standard errors of the means). Data for each chimeric group were generated in two independent experiments with 4 to 9 mice per group.