Molecular and transcriptional basis of bidirectional CD4+ T cell exhaustion in oropharyngeal squamous cell carcinoma

Tumor‐infiltrating CD4+ T cells orchestrate the adaptive immune response through remarkable plasticity, and the expression patterns of exhaustion‐related inhibitory receptors in these cells differ significantly from those of CD8+ T cells. Thus, a better understanding of the molecular basis of CD4+ T cell exhaustion and their responses to immune checkpoint blockade (ICB) is required. Here, we integrated multiomics approaches to define the phenotypic and molecular profiles of exhausted CD4+ T cells in oropharyngeal squamous cell carcinoma (OPSCC). Two distinct immune‐promoting (Module 1) and immunosuppressive (Module 2) functional modules in tumor‐infiltrating CD4+ T cells were identified, and both the immune‐promoting function of Module 1 cells and immunosuppressive function of Module 2 cells were positively associated with their corresponding exhaustion states. Furthermore, the application of ICBs targeting effector CD4+ T cells in Module 1 (αPD‐1) and Treg cells in Module 2 (αCTLA‐4) in mouse models could help reinvigorate the effector function of Module 1‐exhausted CD4+ T cells and reduce the immunosuppressive function of Module 2‐exhausted CD4+ T cells, ultimately promoting OPSCC tumor regression. Taken together, our study provides a crucial cellular basis for the selection of optimal ICB in treating OPSCC. Tumor‐infiltrating CD4+ T cells in OPSCC were categorized into the immune‐promoting module (Module 1) and the immunosuppressive module (Module 2).The functions of Module 1 and Module 2 were positively associated with the T cell exhaustion states.Blocking the exhaustion progression of the bidirectional modules of CD4+ T cells alter the functional balance between Module 1 and Module 2 exhausted cells.