Low TCR Binding Strength Results in Increased Progenitor-like CD8+ Tumor-Infiltrating Lymphocytes

• Published in: Cancer immunology research 2023-05, Vol.11 (5), p.570-582
• Main Authors: Hay, Zachary L Z, Knapp, Jennifer R, Magallon, Roman E, O'Connor, Brian P, Slansky, Jill E
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Neoplasm - metabolism; CD8-Positive T-Lymphocytes; Lymphocytes, Tumor-Infiltrating; Mice; Mice, Transgenic; Neoplasms - metabolism; Peptides - metabolism; Receptors, Antigen, T-Cell; T-Lymphocytes; Tumor Microenvironment
• ISSN: 2326-6066; 2326-6074
• DOI: 10.1158/2326-6066.CIR-22-0761

T-cell receptor (TCR) binding strength to peptide-MHC antigen complex influences numerous T-cell functions. However, the vast diversity of a polyclonal T-cell repertoire for even a single antigen greatly increases the complexity of studying the impact of TCR affinity on T-cell function. Here, we determined how TCR binding strength affected the protein and transcriptional profile of an endogenous, polyclonal T-cell response to a known tumor-associated antigen (TAA) within the tumor microenvironment (TME). We confirmed that the staining intensity by flow cytometry and the counts by sequencing from MHC-tetramer labeling were reliable surrogates for the TCR-peptide-MHC steady-state binding affinity. We further demonstrated by single-cell RNA sequencing that tumor-infiltrating lymphocytes (TIL) with high and low binding affinity for a TAA can differentiate into cells with many antigen-specific transcriptional profiles within an established TME. However, more progenitor-like phenotypes were significantly biased towards lower affinity T cells, and proliferating phenotypes showed significant bias towards high-affinity TILs. In addition, we found that higher affinity T cells advanced more rapidly to terminal phases of T-cell exhaustion and exhibited better tumor control. We confirmed the polyclonal TIL results using a TCR transgenic mouse possessing a single low-affinity TCR targeting the same TAA. These T cells maintained a progenitor-exhausted phenotype and exhibited impaired tumor control. We propose that high-affinity TCR interactions drive T-cell fate decisions more rapidly than low-affinity interactions and that these cells differentiate faster. These findings illustrate divergent forms of T-cell dysfunction based on TCR affinity which may impact TIL therapies and antitumor responses.