LAG3 and PD1 synergize on CD8+ T cells to drive T cell exhaustion and hinder autocrine IFN gamma-dependent anti-tumor immunity

Combined nivolumab (anti-PD1) and relatlimab (anti-LAG3) have shown enhanced effectiveness in melanoma patients. However, how these two receptors work together to hinder anti-tumor immunity remains unclear. Our study demonstrates that PD1/LAG3-deficient CD8+ T cells with more effectively clearing tumors and survive longer in melanoma mouse models. These PD1/LAG3-deficient CD8+ T cells have unique transcriptional profiles, broad TCR clonality, and enriched effector-like and interferon-responsive genes, leading to increased IFN gamma release indicating functionality. PD1 and LAG3 together drive T cell exhaustion, with a significant impact on TOX modulation. Mechanistically, autocrine IFN gamma signaling is crucial for enhancing anti-tumor immunity in PD1/LAG3-deficient CD8+ T cells, providing insights into the enhanced efficacy of combined PD1 and LAG3 targeting. We employed single-cell RNA sequencing to profile CD8 cells from polyclonal/pMEL mice, both with and without single or double deficiencies of PD1 or LAG3. This comprehensive approach aimed to gain a deeper understanding of the enhanced efficacy observed in the melanoma model.