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. 2019 Aug;189(8):1594–1607. doi: 10.1016/j.ajpath.2019.04.018

Figure 3.

Figure 3

CD8+ immune T cells attach to and invade into Toxoplasma gondii cysts in the brains of infected mice. Athymic nude mice were infected orally with 20 cysts of the ME49 strain of T. gondii and treated with sulfadiazine beginning at 11 days after infection to establish a chronic infection by forming cysts in their brains. AF: CD8+ T cells (3.5 × 106 cells) purified from the spleens of infected BALB/c mice were injected intravenously from a tail vein; and 2 to 3 days later, their brains were applied for immunohistochemical staining for T. gondii (brown; A, C, E, and F) or bradyzoite-specific BAG1 (brown; B and D) and CD3 (red), the T-cell marker. A and B: T cells attached on the surface of cyst-containing cells. CF: T cells that had migrated halfway through the cyst wall (arrows). F: T cells that completely penetrated into the cysts were detected (arrowheads). GK: Confocal microscopy with staining for T. gondii (green) and CD3 (red) was also performed on their brains. G: The bent of the cyst wall inward at the site of CD8+ T-cell attachment (arrow), shown at higher magnification in H. H: Leakage of T. gondii materials at the site of CD8+ T-cell attachment (arrows). IK: Confocal images of the T cell that was halfway in the invasion into a cyst. Another group of infected and sulfadiazine-treated nude mice received CD8+ normal T cells from uninfected BALB/c mice, and the immunohistochemical studies were performed on their brains in the same manner. L: The frequencies of T. gondii cysts associated with the T cells were calculated for each of these two groups of mice that had received the normal or immune CD8+ T cells. Data are expressed as means ± SEM in each group (L). P < 0.05 (U-test). Original magnification: ×400 (AF); ×1000 (GK). SCID, severe combined immunodeficiency; WT, wild type.