Figure 7

Flow cytometric assessment of the timecourse of neutrophil and inflammatory monocyte infiltration during acute infection. Brain-infiltrating leukocytes (BILs) were prepared from uninfected (A-C) mice or from mice infected with Theiler's murine encephalomyelitis virus (TMEV) for 12 h (D-F), 18 h (G-I), or 24 h (J-L). Cells were stained with antibodies against CD45, CD11b, Gr1 (Ly6C/G) and 1A8 (Ly6G) and analyzed by flow cytometry. Essentially no Gr1⁺ (B) or 1A8⁺ cells (C) were observed in uninfected mice and the forward scatter (FSC) vs side scatter (SSC) plot showed a clear absence of the larger, more granular cells present at later time points (A). In contrast, TMEV-infected mice exhibited both CD11b⁺⁺Gr1⁺ inflammatory monocytes and CD11b⁺⁺⁺1A8⁺ neutrophils as early as 12 hpi (D-E), with inflammatory monocytes outnumbering neutrophils (E, F). Both of these populations increased in number by 18 hpi (G-I). Neutrophils continued to increase in the infiltrate by 24 hpi (K, L) while inflammatory monocytes began to decrease at this time point (K, L). The granular profile of neutrophils was also clearly present by FSC and SSC at 24 hpi (J). Results are representative of more than 20 mice at each timepoint.