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. 2014 Apr 10;10(4):e1004047. doi: 10.1371/journal.ppat.1004047

Figure 1. Differences in pH sensitivity of two fluorescent markers can be used to distinguish parasites that have been phagocytosed from those that actively invade host cells.

Figure 1

Fluorescence intensity of mCherry-expressing cpsII parasites labeled with CellTrace Violet and incubated overnight at varying pH in buffer solutions consisting of citric acid and disodium phosphate [93] was measured by flow cytometry (a). Violet and mCherry fluorescence of immortalized murine bone marrow-derived macrophages exposed to Violet-labeled, mCherry-expressing cpsII parasites pre-treated with DMSO (top) or the irreversible inhibitor of invasion 4-p-bpb (bottom) 1 hour and 18 hours following exposure to parasites, measured by flow cytometry (b). Images of mCherry+veViolet+ve and mCherry+veViolet−ve bone marrow-derived macrophages 18 hours following exposure to Violet-labeled, mCherry-expressing cpsII parasites pre-treated with 4-p-bpb or DMSO (c). Violet and mCherry fluorescence of cells isolated from the PECS of mice 18 hours post-administration of 106 DMSO-treated or 4-p-bpb-treated parasites (d). Cytospin analysis was performed on Violet+ve cells isolated by FACS sorting, obtained from the PECS of a mouse 18 hours after vaccination with Violet-labeled cpsII parasites (e). Images of mCherry+veViolet+ve and mCherry+veViolet−ve cells isolated from the PECS of mice 18 hours post-administration of 106 DMSO-treated or 4-p-bpb-treated Violet-labeled, mCherry-expressing cpsII parasites (f).