Figure 4.

GR1⁺ cells in bone marrow sense VSV. A, bone marrow from C57Bl/6 mice was left undepleted (none) or depleted of macrophages, NK, CD8, CD4, or GR1⁺ cells and cocultured with B16ova cells +/− VSV (MOI 0.1) as in Fig. 1A. Forty-eight hours after addition of VSV, supernatants were assayed for IL-28. B, C57Bl/6 (3 mice/group) bearing B16ova tumors were injected intratumorally with 5 × 10⁸ pfu of VSV (filled column) or PBS (opened column). Tumors (i) and draining lymph node (LN; ii and iii) were harvested at times shown and analyzed for (i) neutrophils (CD11b⁺GR1⁺F4/80⁻), CD11b⁺GR1⁺ (ii), or plasmacytoid dendritic cells (CD11b⁺GR1⁺PDCA⁺; iii). Infiltrates in tumors injected intratumorally with heat-inactivated VSV as a negative control were directly comparable with those tumors treated with PBS (data not shown). TM, tumor; DC, dendritic cells. C, C57Bl/6 bone marrow was left undepleted (i) or depleted of macrophages (ii) or GR1⁺ cells (iii), and cocultured with B16ova with VSV (MOI, 0.1) and neutralizing anti-VSV antibody (NAb) as in Fig. 1A. Forty-eight hours after the addition of VSV, cell survival was visualized or quantified by MTT assay (D). *, P < 0.05; **, P < 0.01; ***, P < 0.001.