FIG 8.

Immune sera identify T. cruzi in myocytes in situ. (A) Parasite-specific antibody responses in paretic T. cruzi-infected mice (10 months p.i.). (B) Immunofluorescence localization of an amastigote nest (white arrow), using serum from a chronically infected mouse. Two serial sections of quadriceps muscle from a paretic T. cruzi-infected mouse were stained with either serum from the same mouse or serum from an age-matched uninfected mouse. The results were confirmed on the same tissue with sera from two other chronically T. cruzi-infected mice. Bars, 7 μm (left), 50 μm (middle), and 7 μm (right). (C) Absence of antibody deposits in systemic necrotizing vasculitis lesions in skeletal muscle. Sections of quadriceps muscle from a paretic T. cruzi-infected mouse were stained with serum from a paretic T. cruzi-infected mouse or an age-matched uninfected mouse. Slides were then stained with an anti-mouse IgG secondary antibody (red) and counterstained with DAPI (blue). Confocal immunofluorescence images are superimposed on bright-field images. i and iii, fields with systemic necrotizing vasculitis lesions; ii, T. cruzi within a skeletal muscle fiber (the arrow denotes an arteriole).