Cytotoxic T lymphocyte (CD8-positive T cell) (CD8+ T cell)

CD8-positive T lymphocytes—also known as cytotoxic T cells—are a large subset of T cells expressing the CD8 transmembrane glycoprotein as a co-receptor alongside the T cell receptor (TCR)[2][4][5]. CD8+ T cells are essential mediators of cytotoxic cellular immunity; their function is to recognize antigens presented via major histocompatibility complex class I (MHC I) on the surface of infected or malignant cells and to directly kill these target cells through granzyme/perforin-induced apoptosis or through Fas/FasL pathway engagement[1][3]. These lymphocytes are critical for immune surveillance against tumors and clearance of pathogen-infected cells, and are a principal effector cell population in successful anti-tumor immunotherapies such as immune checkpoint inhibitors[5][7]. Subsets of CD8+ T cells exist with various effector, memory, or exhausted phenotypes, shaping immune outcomes in infections, cancer, and autoimmunity. CD8 itself (the molecule) is not typically considered a therapeutic drug target, but therapies frequently aim to boost or modulate the activity of CD8+ T cells. Note: "CD8 expressing lymphocytes" as a target is not a single molecule but a population of immune cells defined by surface marker expression. The correct canonical molecular targets would be either the CD8 alpha (CD8A) or CD8 beta (CD8B) chains, or the T cell receptor complex. CD8+ T cells themselves are not a molecular drug target but are a cell population manipulated by immunotherapies[2][4][7].

Other names

Cytotoxic T lymphocyteCD8 T cellCD8-positive T cellCD8+ T lymphocyteCytotoxic T lymphocyte (CTL)

Enhancement (or inhibition) of cytotoxic T cell activity (e.g., checkpoint blockade restores CD8+ T cell function in tumor microenvironments); Antigen-specific cytotoxicity (engineered TCR/CAR constructs); Cytokine-driven expansion or activation