Figure 3.

Leukocytes in the brain 48 h post infection. The recruitment of leukocytes was quantified by multiparametric flow cytometric analysis in the brains of C57BL/6J mice collected 48 h post intracranial infection with 3 × 10⁴ CFU of S. pneumoniae TIGR4. As control, a group of mice was injected with bacterial growth medium. (A) Gating strategy adopted for the identification of leukocyte populations in brain of mice. Lymphocytes (CD45^hiCD3⁺), NKs cells (CD45^hiCD3⁻NKp46⁺), neutrophils (CD45^hiCD11b^hiLy6G⁺), monocytes (CD45^hiCD11b^hiLy6G⁻Ly6C⁺), and macrophages (CD45^hiCD11b^hiF4/80⁺) were detected. (B) Percentages (%) of cell populations detected in brain of mice infected with S. pneumoniae TIGR4 or injected with bacterial growth medium. Infection with TIGR4 induced the entry in the brain of about 4% lymphocytes, 5% NK cells, 27% neutrophils, 21% monocytes, and 19% macrophages, all evaluated on CD45⁺ cells. In control group all cell populations detected were ≤ 0.7% of CD45⁺ cells. Data are from four independent experiments with 3–6 animals/group. Bars represent mean ± SEM. Two tailed Mann-Whitney test was used for comparison between infected and control group and asterisks indicate statistical significance (^***P < 0.001).