IMMUNOLOGY2026™ Conference Recordings For Attendees-Bystander activation in CD8 memory T cells is an innate program that is standalone from, yet influences TCR and TCR-driven responses

Bystander activation in CD8 memory T cells is an innate program that is standalone from, yet influences TCR and TCR-driven responses

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Video Summary

The talk examined how memory CD8 T cells become activated through either conventional TCR recognition of antigen or “bystander” activation driven by cytokines like IL-12, IL-15, and IL-18. Bystander cells can still produce interferon-gamma, proliferate, and even kill targets via stress-induced NKG2D ligands, despite not recognizing antigen through their TCR. The speaker tested whether TCR signaling is required for bystander activation by using NFAT inhibitors, inducible TCR-alpha deletion, and CD3epsilon CRISPR disruption. Across these models, bystander interferon-gamma and activation markers remained intact, indicating bystander activation is largely TCR-independent. They also found PD-1, a checkpoint known to regulate TCR responses, did not meaningfully restrain bystander activation. However, stable TCR expression seemed necessary for PD-1 upregulation during bystander responses, suggesting crosstalk between the two programs. Overall, the data support two distinct CD8 activation modes—adaptive and innate-like—with unresolved questions about their mechanisms and functional consequences.

Meta Tag

Date April 19, 2026 8:30 AM - 8:45 AM

Room 153AB

Session Dynamic Control of T Cell Activation

Speaker Nicholas Maurice

Track Immune Response Regulation: Cellular Mechanisms (IRC)

Year 2026

Keywords

memory CD8 T cells

bystander activation

TCR-independent

cytokines IL-12 IL-15 IL-18

PD-1 regulation

April 19, 2026 8:30 AM - 8:45 AM

153AB

Dynamic Control of T Cell Activation

Nicholas Maurice

Immune Response Regulation: Cellular Mechanisms (IRC)

2026