Exhausted CD8 T cells downregulate the IL-18 receptor and become unresponsive to inflammatory cytokines and bacterial co-infections.

Published

Journal Article

During many chronic infections virus-specific CD8 T cells succumb to exhaustion as they lose their ability to respond to antigenic activation. Combinations of IL-12, IL-18, and IL-21 have been shown to induce the antigen-independent production of interferon (IFN)-γ by effector and memory CD8 T cells. In this study we investigated whether exhausted CD8 T cells are sensitive to activation by these cytokines. We show that effector and memory, but not exhausted, CD8 T cells produce IFN-γ and upregulate CD25 following exposure to certain combinations of IL-12, IL-18, and IL-21. The unresponsiveness of exhausted CD8 T cells is associated with downregulation of the IL-18-receptor-α (IL-18Rα). Although IL-18Rα expression is connected with the ability of memory CD8 T cells to self-renew and efflux rhodamine 123, the IL-18Rα(lo) exhausted cells remained capable of secreting this dye. To further evaluate the consequences of IL-18Rα downregulation, we tracked the fate of IL-18Rα-deficient CD8 T cells in chronically infected mixed bone marrow chimeras and discovered that IL-18Rα affects the initial but not later phases of the response. The antigen-independent responsiveness of exhausted CD8 T cells was also investigated following co-infection with Listeria monocytogenes, which induces the expression of IL-12 and IL-18. Although IL-18Rα(hi) memory cells upregulated CD25 and produced IFN-γ, the IL-18Rα(lo) exhausted cells failed to respond. Collectively, these findings indicate that as exhausted T cells adjust to the chronically infected environment, they lose their susceptibility to antigen-independent activation by cytokines, which compromises their ability to detect bacterial co-infections.

Full Text

Duke Authors

Cited Authors

  • Ingram, JT; Yi, JS; Zajac, AJ

Published Date

  • September 29, 2011

Published In

Volume / Issue

  • 7 / 9

Start / End Page

  • e1002273 -

PubMed ID

  • 21980291

Pubmed Central ID

  • 21980291

Electronic International Standard Serial Number (EISSN)

  • 1553-7374

International Standard Serial Number (ISSN)

  • 1553-7366

Digital Object Identifier (DOI)

  • 10.1371/journal.ppat.1002273

Language

  • eng