Fig 2: Sentinel macrophages mediate capture of incoming viruses at the injection site during subcutaneous challenge.(A) Images of footpad cryosections from B6 mice 15 min after intrafootpad (i.f.p.) administration of murine leukemia virus (MLV) Gag-GFP virus particles (green). Macrophages and dendritic cells (DCs) were identified using antibodies to CD169 (blue) and CD11c (red), respectively. Green arrows denote MLV-laden CD169+ macrophages, and white arrows denote contacts between CD169+ macrophages and DCs. (B) Electron tomography of footpads from B6 mice prepared 15 min post-challenge with WT FrMLV. MLV virions can be seen associated with plasma membranes (PM) invaginations of macrophages (mF) as well as via a presumed CD169 tether in the magnified inset. (C) Electron tomography showing synaptic, MLV-containing contacts between macrophages and DCs in footpads of B6 mice at 15 min post-challenge (i.f.p.) WT FrMLV. Green arrowheads indicate macrophage-associated MLV particles, and blue arrowheads indicate DC-associated MLV particles. Scale bars as indicated.

Fig 3: Immunofluorescence analysis. A Representative immunofluorescence images of the paw skin tissue, showing the infiltration of ionized calcium-binding adapter molecule 1 (Iba1)-, CD11c-, and CD206-positive cells in the dermis (surrounded by the dotted line). Scale bar: 50 µm. B Number of Iba1-, CD11c-, and CD206-positive cells in the dermis (n = 6 each). Data are presented as the mean ± SEM. *P < 0.05; **P < 0.01. cKO conditional knockout