CD8TZellen

CD8 T-Zellen, or CD8+ T cells, are a subset of T lymphocytes characterized by the expression of the CD8 co-receptor. They recognize peptide antigens presented by MHC class I molecules on nearly all nucleated cells, enabling them to detect intracellular pathogens and transformed cells. Upon activation by antigen-presenting cells and help from CD4+ T cells, naive CD8+ T cells proliferate and differentiate into effector cytotoxic T cells and memory cells.

Effector CD8+ T cells kill target cells primarily through the perforin-granzyme pathway, releasing cytotoxic granules that induce apoptosis, and through Fas-FasL interactions. They also secrete cytokines such as interferon-gamma and tumor necrosis factor-alpha, which modulate the immune response and inhibit pathogen replication. Activation requires T cell receptor recognition of antigen presented on MHC I, along with co-stimulatory signals (e.g., CD28).

CD8+ T cells can be classified into subsets based on differentiation and trafficking: naive (CD45RA+ CCR7+), central memory (CD45RO+ CCR7+), effector memory (CD45RO+ CCR7-), and tissue-resident memory (often CD103+). In thymic development, they originate as CD4-CD8- double-positive thymocytes that mature into CD8 single-positive cells before emigration.

Clinical significance: CD8+ T cells are central in immunity against intracellular pathogens such as viruses and certain intracellular bacteria, and they play a key role in tumor surveillance. Tumors may evade by downregulating MHC class I. Therapeutically, CD8+ T cells are targeted in cancer immunotherapy, including checkpoint inhibitors that reinvigorate exhausted T cells and adoptive cell therapies such as CAR-T cells, often mediated by or including CD8+ populations.