CD8-positive tumor-infiltrating lymphocyte (CD8+ TIL)

CD8-positive tumor-infiltrating lymphocytes (CD8+ TILs) are a specialized population of cytotoxic T cells that migrate from the blood into the tumor microenvironment to mediate anti-tumor immunity [1, 3]. They recognize tumor-associated antigens presented by Major Histocompatibility Complex (MHC) class I molecules and induce apoptosis in malignant cells through the secretion of perforin, granzymes, and cytokines such as interferon-gamma (IFN-γ) [3, 9]. The density and spatial distribution of CD8+ TILs are critical prognostic and predictive biomarkers; 'hot' tumors with high CD8+ infiltration generally respond better to treatments than 'cold' or 'excluded' tumors [1, 13]. Therapeutic interventions often target these cells to reverse exhaustion—a state of functional impairment caused by chronic antigen exposure—using immune checkpoint inhibitors like anti-PD-1/PD-L1 antibodies [1, 13]. Additionally, adoptive cell therapy (TIL therapy) involves harvesting, expanding, and reinfusing these autologous cells to provide a robust, multi-antigen-targeted attack against advanced cancers [5, 6].

Other names

CD8+ T cellsCytotoxic T lymphocytesCTLsTumor-infiltrating CD8+ T cellsIntratumoral CD8+ T cells

Drugs targeting CD8-positive tumor-infiltrating lymphocytes primarily work by either reinvigorating exhausted T cells through the blockade of inhibitory checkpoints like PD-1/PD-L1 and CTLA-4, or by the ex vivo expansion and reinfusion of these cells in adoptive cell transfer therapies to enhance direct tumor lysis and cytokine-mediated anti-tumor activity.