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.