Checkpoint blockade and the stem-like T cell trade-off.

Area of Science:

• Immunology
• Cancer Biology
• Cellular Immunology

Background:

• Stem-like T cells are essential for sustained anti-tumor immunity during PD1 blockade.
• The mechanisms regulating stem-like T cell maintenance in cancer are not fully understood.

Purpose of the Study:

• To investigate the niche and regulatory mechanisms of stem-like T cells in murine cancer models.
• To define the role of conventional type 1 dendritic cells (cDC1s) and PD1 signaling in stem-like T cell maintenance.

Main Methods:

• High-dimensional 3D-imaging
• Immunological profiling
• Murine cancer models

Main Results:

• cDC1s preserve high-affinity tumor-specific stem-like T cells by providing sustained TCR stimulation and PD-L1/2 co-inhibitory signals.
• PD1 signaling disruption enhances effector T cell expansion but leads to stem-like T cell differentiation and apoptosis.
• Disruption of PD1 signaling ultimately depletes the stem-like T cell pool.

Conclusions:

• cDC1s and PD1 signaling are critical for maintaining the stem-like T cell reservoir necessary for long-term anti-tumor responses.
• Disruption of PD1 signaling may represent a long-term vulnerability in immune checkpoint blockade therapy if tumors are not fully eradicated.