Time course of Mac-1⁺/Gr-1^int cell appearance following MCMV infection. Leukocytes were prepared from FPs (A) and PB (B) of groups of 5 infected BALB/c mice on days 0, 1, 2, 3, and 5 after inoculation with mck-expressing RQ461 or mck-mutant RM461 (inoculum of 1 × 10⁶ PFUs). Mac-1⁺/Gr-1^int cell populations are indicated by the boxed areas. (B) An arrow in the day 3 sample identified the peak in mobilization of the Mac-1⁺/Gr-1^int cells into the bloodstream. (C) Summary of the kinetics of mobilization of Mac-1⁺/Gr-1^int cells into PB and recruitment into FPs.