Figure 2

Flow cytometric assessment of the infiltrate present in the brain of mice acutely infected with Theiler's murine encephalomyelitis virus (TMEV). TMEV-infected (B-G) or sham-infected (A) mice were killed at 18 h post infection (hpi). Brain was collected fresh and processed for the isolation of brain-infiltrating leukocytes (BILs). BILs were stained with antibodies against CD45, CD11b, F4/80, Gr1 (Ly6C/G) and 1A8 (Ly6G) and analyzed by flow cytometry. No CD45^hi cells were observed in sham-infected mice (A). In contrast, TMEV-infected mice exhibited a large population of CD45^hi cells at 18 hpi. Analysis of the CD45^hi cells in BILs from infected mice revealed the presence of CD11b⁺⁺ cells that were also strongly positive for the Gr1 antigen (C) and CD11b⁺⁺⁺ cells that were positive for both the Gr1 antigen (C) and the 1A8 antigen (D). In addition, a population of the Gr1⁺ cells was also positive for F4/80 (E); no 1A8⁺ cells were F4/80⁺ (F). Combined gating revealed that CD45^hiCD11b⁺⁺Gr1⁺ cells were also F4/80⁺ while CD45^hiCD11b⁺⁺⁺Gr1⁺ cells were F4/80^-. Quantitation of neutrophils (CD45^hi1A8⁺Gr1⁺CD11b⁺⁺⁺F4/80^-) and inflammatory monocytes (CD45^hi1A8^-Gr1⁺CD11b⁺⁺F4/80⁺) in BILs from 10 individual mice revealed that about 80% of the CD45^hi cells belonged to one of these populations (G). Error bars in (G) represent 95% confidence intervals; black circles represent individual animals; 10 mice per group were analyzed and the flow plots in (A-F) are representative.