IFNγ is required to increase monocyte numbers and suppress neutrophilia during LCMV infection. Representative plot of intracellular staining for IFNγ in T cells from BM of WT and IFNγ^−/− mice stimulated in vitro 8 days after LCMV infection with LCMV peptide (A) or PMA/ionomycin (B). (C) Representative plot of staining for monocytes (Gr1^lowCD115⁺) and neutrophils (Gr1⁺CD115⁻) in the peripheral blood before LCMV infection and at the indicated days after infection. Numbers of monocytes (D) and neutrophils (E) in the peripheral blood of WT and IFNγ^−/− mice at the indicated days after LCMV infection and M:N ratios in the peripheral blood of these mice (F) are shown. Data in panels D through F represent means ± SEM from 5 mice per group. Numbers of monocytes (G) and neutrophils (H) in the BM of WT and IFNγ^−/− naive mice and LCMV-infected mice 8 days after infection and the M:N ratio in the BM of these mice (I) are shown. Data in panels G through I represent means ± SD from 5 mice per group; BM represents cell numbers per 2 femurs and 2 tibiae. (J) Number of CD8 T cells in the peripheral blood of WT and IFNγ^−/− mice at the indicated days after LCMV infection. (K-L) Percentage of tetramer-binding cells of total CD8 T cells in the peripheral blood (K) and number of tetramer-binding CD8 T cells in BM of WT and IFNγ^−/− mice 8 days after LCMV infection (L). Data in panel J represent means ± SEM from 5 mice per group and data in panels K and L represent means ± SD from 5 mice per group. All data shown are representative of at least 2 independent experiments. *P < .05; **P < .01; ***P < .001.