IFNγ expression correlates with enhanced cytotoxicity in CD8+ T cells
BackgroundCD8+ T lymphocytes (CTLs) act as serial killers of infected or malignant cells by releasing large amounts of interferon-gamma (IFN{gamma}) and granzymes. Although IFN{gamma} is a pleiotropic cytokine with diverse immunomodulatory functions, its precise spatiotemporal regulation and role in CTL-mediated cytotoxicity remain incompletely characterized. MethodsUsing wild-type (WT) and granzyme B-mTFP knock-in mice, we combined in vitro approaches, including T-cell isolation and culture, plate-bound anti-CD3e stimulation, degranulation assays, flow cytometry, immunofluorescence, and structured illumination microscopy, to investigate IFN{gamma} dynamics in CTLs. ResultsIFN{gamma} expression in CTLs was rapid, transient, and strictly dependent on T-cell receptor (TCR) activation. We identified two functionally distinct IFN{gamma}-producing subsets: IFN{gamma}high (IFN{gamma}hi) and IFN{gamma}low (IFN{gamma}lo) CTLs. IFN{gamma}hi CTLs exhibited an effector/effector memory phenotype, significantly elevated CD107a surface expression (a marker of lytic granule exocytosis), and pronounced colocalization with cis-Golgi and granzyme B compared to IFN{gamma}lo CTLs. Furthermore, CRTAM, an early activation marker, correlated with IFN{gamma} expression in naive CTLs. ConclusionOur findings establish a link between elevated IFN{gamma} production and enhanced CTL cytotoxicity, implicating CRTAM as a potential regulator of early CTL activation and IFN{gamma} induction. These insights provide a foundation for optimizing T cell-based immunotherapies against infections and cancers.