Penetration of CD8+ Cytotoxic T Cells into Large Target, Tissue Cysts of Toxoplasma gondii, Leads to Its Elimination

Ashish Tiwari, Rancie Hannah, J. Lutshumba, Eri Ochiai, Louis M. Weiss, Yasuhiro Suzuki

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


CD8+ cytotoxic T cells kill target cells through direct cell-cell contact. However, it remains unclear how these T cells eliminate a target of large mass. We investigated how CD8+ T cells remove tissue cysts of Toxoplasma gondii, which can grow to the size of >50 μm in diameter within infected cells. Notably, immunohistologic analyses in the brains of infected mice visualized the presence of numbers of CD8+ immune T cells that had migrated halfway through the cyst wall as well as T cells located fully within the cysts. Perforin was required for their invasion and cyst elimination. Cysts invaded by the T cells displayed morphologic deterioration and destruction. Within these deteriorated cysts, granular structures intensely positive for granzyme B were detected in association with T. gondii bradyzoites. Furthermore, the bradyzoites within the destroyed cysts were located within accumulated ionized calcium binding adaptor molecule 1 (Iba1)-positive microglia and Ly6C+ macrophages, suggesting that these phagocytes had phagocytosed those organisms for their eradication. The present study uncovered a previously unappreciated capability of CD8+ cytotoxic T cells to penetrate into a large target, T. gondii cysts, for their elimination. This invasive capability of CD8+ cytotoxic T cells in collaboration with phagocytes appears to be a powerful effector mechanism that functions against not only T. gondii cysts but also other large targets, including solid cancers.

Original languageEnglish
Pages (from-to)1594-1607
Number of pages14
JournalAmerican Journal of Pathology
Issue number8
StatePublished - Aug 2019

Bibliographical note

Publisher Copyright:
© 2019 American Society for Investigative Pathology

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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