Figure 1. Myeloid-specific deletion of Ttp increases immune response and resistance against invasive infection with S. pyogenes.

(A) Survival of TTP^fl/fl and TTP^ΔM mice (n = 8/genotype) during s.c. infection with 3 × 10⁸ CFU S. pyogenes. Animals were monitored for 5 days. Kaplan-Meier survival curves are shown. **P < 0.01, by Mantel-Cox test. (B) The area of inflammation was determined 48 hours p.i. Two independent experiments were pooled (n = 11 TTP^fl/fl and n = 16 TTP^ΔM mice in total). Error bars represent the mean. **P < 0.01, by unpaired Student’s t test. (C) H&E-stained tissue sections of flanks from TTP^fl/fl and TTP^ΔM mice 24 and 48 hours p.i. were graded for leukocyte infiltration, necrotic tissue abundance, inflammation, PMN infiltration, and vascular congestion. Scores were combined for overall grading. Error bars indicate the median. *P < 0.05, by Mann-Whitney U test. (D) Representative H&E- (left panel), Gr-1– (middle panel), and S. pyogenes–stained (right panel) tissue sections of flanks from TTP^fl/fl (top) and TTP^ΔM (bottom) animals 48 hours p.i. Arrows indicate Gr-1–stained cells. Note an increased infiltrate and containment of bacteria in tissues from TTP^ΔM mice. Original magnification, ×2.5 and ×20 (insets in H&E-stained images). Scale bars: 200 μm. (E) Bacterial loads in the blood, liver, and lesions from TTP^fl/fl and TTP^ΔM mice infected with 3 × 10⁸ CFU S. pyogenes. Samples were taken 48 hours p.i., and the bacterial load was determined. Dot plots represent a pool of 2 independent experiments (n = 11 TTP^fl/fl and n = 14 TTP^ΔM mice for organs; n = 13 TTP^fl/fl and n = 11 TTP^ΔM mice for lesions). Error bars indicate the median. *P < 0.05 and **P < 0.01, by Mann-Whitney U test.