CD8Tlymfosyytit

CD8Tlymfosyytit, typically referred to in English as CD8 T lymphocytes or CD8+ T cells, are a subset of T lymphocytes defined 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 cells harboring intracellular pathogens or undergoing malignant transformation.

Developmentally, CD8+ T cells arise in the thymus from double-positive thymocytes and mature into CD8+ single-positive cells. In the periphery, naive CD8+ T cells circulate through secondary lymphoid organs and become activated when their T cell receptor engages a cognate antigen presented by an antigen-presenting cell, with additional co-stimulatory signals and cytokines such as IL-2.

Activated CD8+ T cells differentiate into cytotoxic T lymphocytes (CTLs) that kill target cells through several mechanisms. They release cytotoxic granules containing perforin and granzymes, induce apoptosis via Fas-FasL interactions, and secrete cytokines such as interferon-gamma and TNF-α to coordinate the immune response. After clearance of the threat, CD8+ T cells contract and memory subsets persist for faster responses upon re-exposure to the antigen.

CD8+ T cells play a central role in defending against viral infections and malignancies, and they are a major focus of cancer immunotherapies, including approaches that unleash or enhance their activity. Regulation by checkpoints such as PD-1 and CTLA-4 helps prevent excessive tissue damage, but can also limit effective responses in chronic infections or cancer.