Profiling of leukocyte subpopulation. Cell surface markers conjugated with proper fluorochrome, which can differentiate the leukocyte subpopulation, were used to stain the fresh-drawn blood and subjected to FACS as described in “FACS analysis and immunohistochemistry.” (A) Absolute counts of each leukocyte subpopulation with SE bar from each animal were presented. A noticeable reduction of monocytes on day 1 after infection was observed, and thereafter a rebounded pattern to normal level was registered. A slight fluctuation with a trend of gradual increase in lymphocytes during acute infection was seen. A consistent and gradual reduction of neutrophils was documented during the acute period, which returned to uninfected level 14 days after infection. (B) Percentage of lymphocyte subpopulation with SE bar from each animal was presented. P.I. indicates postinfection.