Elevations of Th17.1 Cells ( CXCR3 + CCR6 + T Cells With IL ‐ 17A and IFN ‐γ Production) in Peripheral Blood of Patients With Lung Cancer

ABSTRACT Peripheral T cell profiles reflect antitumour immunity, yet systemic immune shifts often remain confounded by demographic factors. This study aimed to delineate true tumour‐driven T cell alterations in lung cancer. We analysed peripheral blood from 121 lung cancer patients and strictly age‐ and sex‐matched healthy controls using multiparametric flow cytometry, corroborated by human lung cancer spatial transcriptomics (ST). Following demographic standardisation, patients exhibited a systemic T cell priming blockade, characterised by significantly accumulated naïve T cells and depleted effector memory T cells (CD4 + p < 0.01; CD8 + p < 0.0001). Conversely, Th17.1 cells and immune checkpoints (e.g., PD‐1, CTLA‐4) were robustly elevated. Crucially, ST validated a striking intratumoural spatial accumulation of Th17.1 cells. We conclude that the peripheral expansion of Th17.1 cells is a genuine tumour‐driven event that faithfully mirrors local tumour microenvironment remodelling and potential Tertiary Lymphoid Structure (TLS) neogenesis. This positions peripheral Th17.1 profiling as a valuable, noninvasive biomarker for evaluating systemic immunosuppression and guiding personalised immunotherapy.