Figure 3.

Analysis of individual promoter fusions. Individual promoter fusions isolated from frog granulomas in the library screen were analyzed for activity in DMEM, J774 macrophages, and granulomas. Red lines in the FACS histograms represent fluorescence in DMEM; green lines indicate fluorescence in macrophages. Macrophage confocal images are overlays of red (bacterial membrane protein), green [for expression of the green fluorescent protein (GFP) fusion in the promoter constructs], and blue (macrophage nuclear staining). Therefore GFP expression in macrophages renders the bacteria yellow. In the absence of GFP expression, they are red fluorescent. Granuloma confocal images are overlays of red (macrophage nuclear stain) and green (for expression of the GFP promoter fusion). The maps and gaps have minimal fluorescence in laboratory medium. map 85 is fluorescent in both macrophages (yellow) and granulomas (green), whereas the two gaps are fluorescent only in granulomas (green) and not in macrophages (red). map 25 straddles the classification between a map and a gap, being only slightly activated in macrophages (red with faint yellow) and green in the granuloma. (Bars represent 10 microns.)