This prospective observational cohort study investigates the subset-specific metabolic adaptation and functional remodeling of cytotoxic γδT cells in critically ill patients with and without sepsis. Emerging evidence indicates that γδT cells, as a bridge between innate and adaptive immunity, play a critical role in early anti-infection defense during sepsis. However, the functional status and underlying regulatory mechanisms of cytotoxic γδT cells in septic patients remain incompletely understood. Our preliminary single-cell transcriptomic analysis revealed that cytotoxic γδT cells from septic patients exhibit significant alterations in cytotoxicity-associated molecules (GZMB, PRF1, GNLY) and mitochondrial oxidative phosphorylation (OXPHOS) pathway genes, particularly COX6C, which correlates with cytotoxic effector molecule expression. This study aims to systematically characterize the proportion, cytotoxicity, and mitochondrial metabolic function of circulating cytotoxic γδT cells across three cohorts: healthy controls, critically ill non-septic patients, and critically ill septic patients. By integrating flow cytometry, mitochondrial function assays, and functional validation experiments, we seek to elucidate the role of COX6C-mediated mitochondrial metabolic abnormalities in cytotoxic γδT cell dysfunction, providing theoretical basis for understanding immune dysregulation in sepsis and identifying novel therapeutic targets.
Age ≥ 18 years.
No acute or chronic major diseases.
Provide written informed consent.
Age ≥ 18 years.
Age < 18 years.
Known immunodeficiency, HIV infection, active hematologic malignancy, or history of hematopoietic stem cell or solid organ transplantation within the past 3 months.
Receipt of T-cell-targeted immunosuppressive therapy (e.g., antithymocyte globulin, calcineurin inhibitors, mycophenolate mofetil, methotrexate, or high-dose corticosteroids >1 mg/kg/day prednisone equivalent) before ICU admission or within 24 hours after ICU admission.
Use of immune checkpoint inhibitors (e.g., anti-PD-1/PD-L1/CTLA-4 antibodies) within the past 6 weeks.
The study population comprises three distinct groups: healthy volunteers, non-septic critically ill patients, and septic critically ill patients admitted to the intensive care unit. Sepsis is defined according to the Sepsis-3 criteria (infection with an acute increase in SOFA score ≥2 points), while critical illness is based on standard ICU admission criteria. All participants must be aged ≥18 years and provide written informed consent (from the participant or a legally authorized representative for those unable to consent). Key exclusion criteria include known immunodeficiency, recent use of T-cell-targeted immunosuppressants or immune checkpoint inhibitors, expected ICU stay \<24 hours, pregnancy, active major bleeding, or inability to obtain consent. Consecutive enrollment will take place at the Department of Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, with follow-up through 90 days after enrollment.
Cohort
Prospective
Not listed
Change in the Proportion of Cytotoxic γδT Cells (TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺) Among Total γδT Cells
Flow cytometric quantification of the frequency of Cytotoxic γδT cells, defined as TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺ cells, as a percentage of total γδT cells (TCRγδ⁺) in peripheral blood. This subset represents the cytotoxic effector population critical for early anti-infection defense.
Change in COX6C Expression in Cytotoxic γδT Cells
Measurement of COX6C (mitochondrial respiratory chain complex IV subunit) expression levels in Cytotoxic γδT cells (TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺) at the mRNA level (by single-cell RNA sequencing) and protein level (by flow cytometry).
Change in Cytotoxic Molecule Expression in Cytotoxic γδT Cells
Flow cytometric quantification of the mean fluorescence intensity (MFI) of cytotoxic effector molecules including Granzyme B (GZMB), Perforin (PRF1), and Granulysin (GNLY) in Cytotoxic γδT cells (TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺).
Change in Mitochondrial Mass in Cytotoxic γδT Cell
Flow cytometric quantification of mitochondrial mass using MitoTracker Green FM staining in Cytotoxic γδT cells (TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺).
Change in Mitochondrial Membrane Potential (TMRE) in Cytotoxic γδT Cells
Flow cytometric quantification of mitochondrial membrane potential using tetramethylrhodamine ethyl ester (TMRE) staining in Cytotoxic γδT cells (TCRγδ⁺GZMB⁺PRF1⁺GNLY⁺).
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