Figure 7.

Both cysts formed within neurons and astrocytes were destroyed by CD8⁺ immune T cells, and the destruction of the cysts was associated with accumulation of Iba1⁺ microglia and Ly6C⁺ inflammatory macrophages. Nude mice were infected orally with 20 cysts of the ME49 strain of Toxoplasma gondii and treated with sulfadiazine beginning at 11 days after infection to establish a chronic infection by forming cysts in their brains. 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. A and B: Destroyed cysts (brown) associated with the presence of diffuse NeuN (blue; A) and glial fibrillary acidic protein (GFAP; green; B). C and D: Accumulation of Iba1⁺ microglia (red) and Ly6C⁺ blood-derived macrophages (green) is associated with demolished cysts (brown). Arrowheads indicate T. gondii parasites that maintain a clear morphology. Arrows indicate the representatives of the parasites that had already been destroyed and lost a clear morphology of the parasite. E: The differences in the frequencies of an accumulation of Ly6C⁺ macrophages to morphologically destroyed and intact cysts. ^∗∗∗P < 0.001. Original magnification, ×400 (A–D).