Plasmodium-infected blood cells analyzed and sorted by flow fluorimetry with the deoxyribonucleic acid binding dye...

Red cells from Plasmodium berghei infected mouse blood can be sorted on the basis of their DNA content with the bisbenzimidazole dye 33258 Hoechst. The optimal conditions for dye uptake have been established and with these conditions uninfected cells are nonfluorescent and can be completely separated from infected cells which exhibit fluorescence in almost direct proportion to the number of parasite nuclei (i.e. DNA) they contain. The number of fluorescent cells detected and their fluorescence intensity is shown to be dependent on the dye concentration and the incubation medium being used. At least a proportion of the infected cells sorted from each fluorescence peak in the cell distribution retain their infectivity in vivo with some, but not all, conditions of labeling. This technique is being used to separate minor cell populations from infected blood for biochemical and immunochemical analyses and to screen human samples for malaria infected cells.