The use of bioluminescent:fluorescent T. cruzi reporter strains to monitor tissue microenvironment in the colon during infection (A) Differential recruitment of T cells to closely localised T. cruzi CLBR-Luc:NeonGreen chronic stage (121 dpi) infection foci in a C3H/HeN mouse colon. Smooth muscle wall sections were prepared from colonic whole mounts, following bioluminescence-guided excision, and screened using a Zeiss LSM880 confocal microscope to localise fluorescent infection foci [19–21] (Materials and Methods). The image expansions show three closely localised infection foci, only one of which has triggered recruitment of T cells. Parasites, green (fluorescence); DNA, cyan (Hoechst 33342); CD4⁺ T cells, magenta. (B) Chronic stage (230 dpi) T. cruzi CLBR-Luc:NeonGreen infections of colonic smooth muscle in the context of local enteric neurons. C3H/HeN tissue sections were prepared as above. Neurons, magenta (TuJ1+). (C) A whole mount colon tissue section from a C3H/HeN mouse infected with T. cruzi JR-Luc:NeonGreen imaged by fluorescence microscopy, showing parasites (green) in the myenteric nerve plexus (magenta) (139 dpi). The inset (left) shows the proximal colon bioluminescence image that was used to guide tissue excision and fluorescent imaging of infection foci at single cell resolution (Materials and Methods). (D) Whole mount colonic tissue obtained from an immunocompromised SCID mouse during a fulminant infection with T. cruzi CLBR-Luc:NeonGreen (21 dpi) at the level of the myenteric nerve plexus (unlabelled).