Fig 3. F4/80^hiCD11b^lo MPs are located in close proximity to white pulp vasculature and possess angiogenic properties.

F4/80^hiCD11b^lo cells (FITC-dextran, green; yellow arrows) identified in fresh frozen sections as located either in or bordering the white pulp (A,B). Red pulp F4/80⁺ macrophages are also shown (white). F4/80^hiCD11b^lo cells (FITC-dextran, green) were found in close association with endothelial cells (C, E; Meca-32, magenta) but not follicular dendritic cells (D; FDCM1, red). High magnification image of area depicted by yellow circle in e (F). All sections were counterstained with DAPI (blue). Scale bars = 100 microns. F4/80^hiCD11b^lo cells, but not other splenic MPs tested, drive SVEC4–10 endothelial cell tube formation on a gelled basement membrane extract (G). Representative images are shown. An optimised cocktail of growth factors (EGM) was used as a positive control. Quantitative analysis of SVEC4–10 mean loop area (H) and difference in tube length (I), in the presence of each MP population or control growth factors. Mean loop area in the absence of growth factors or MPs is shown as a dotted line in h. *p = 0.05, **p = 0.02. Images were analysed using WimTube software and data are expressed as mean ± SEM from at least three independent experiments.