Expression of the DNA-Binding Factor TOX Promotes the Encephalitogenic Potential of Microbe-Induced Autoreactive CD8⁺ T Cells

Infections are thought to trigger CD8⁺ cytotoxic T lymphocyte (CTL) responses during autoimmunity. However, the transcriptional programs governing the tissue-destructive potential of CTLs remain poorly defined. In a model of central nervous system (CNS) inflammation, we found that infection with lymphocytic choriomeningitis virus (LCMV), but not Listeria monocytogenes (Lm), drove autoimmunity. The DNA-binding factor TOX was induced in CTLs during LCMV infection and was essential for their encephalitogenic properties, and its expression was inhibited by interleukin-12 during Lm infection. TOX repressed the activity of several transcription factors (including Id2, TCF-1, and Notch) that are known to drive CTL differentiation. TOX also reduced immune checkpoint sensitivity by restraining the expression of the inhibitory checkpoint receptor CD244 on the surface of CTLs, leading to increased CTL-mediated damage in the CNS. Our results identify TOX as a transcriptional regulator of tissue-destructive CTLs in autoimmunity, offering a potential mechanistic link to microbial triggers. Little is known about the transcriptional programs that drive the tissue destructive capacity of effector CD8⁺ T cells during autoimmunity. In an animal model of CNS inflammation, Page et al. demonstrate that expression of the DNA-binding factor TOX promotes the encephalitogenic potential of pathogen-primed CD8⁺ T cells and that TOX expression is determined by the microbial context of CTL priming.