Figure 5. Calprotectin supports S. aureus infection of the heart while promoting neutrophil recruitment.

Mice were placed on high Mn diet (A, B, D) or control diet (C–K) for 5–8 weeks and infected with WT S. aureus for various timepoints (A) or four days (B–K). (A) Heart bacterial burdens. N = 3 (2 hour, S100a9^−/− 96 hour); N = 4 (4 and 24 hour); N = 2 (WT 96 hour). (B) Heart abscesses. N = 4 (WT); N = 3 (S100a9^−/−). (C) Histopathology of infected hearts. Scale bar is 100 μM. (D) Flow cytometry quantification of Ly6G⁺CD11b⁺ cells from hearts. Previous gate, live cells. N = 4 (high Mn groups), 3 (control groups), 2 (mock). (E) Heart bacterial burdens following treatment with anti-Ly6G or isotype control antibodies. N = 9 (WT depleted), 10 (all other groups). (F) Heart bacterial burdens from S100a9^−/− mice transplanted with WT or S100a9^−/− bone marrow (BM). (G–H) Heart bacterial burdens from WT and Tlr4^−/− mice (G) or Ager^−/− mice (H). (I) Ly6G⁺CD11b⁺ cells following BM transplantation of a 1:1 mix of WT congenic BM (CD45.1) and S100a9^−/− BM (CD45.2) into WT mice. Previous gate, CD45⁺ cells. Left, representative flow plot. Right, quantification of neutrophil percentages. N = 3. (J) Mean fluorescence intensity of CD11b on Ly6G⁺ WT and S100a9^−/− cells. N = 7 (WT), 5 (S100a9^−/−). (K) Heart bacterial burdens from WT mice transplanted with WT or S100a9^−/− BM. (A–K) Bars depict median and interquartile range. ns, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001 by Mann-Whitney (A, D); unpaired t-test (E–K). See also Figures S3 & S4.