Tcellemediert

Tcellemediert (T-cell mediated immunity) refers to immune responses that are mediated by T lymphocytes rather than by antibodies produced by B cells. It forms a central component of cell-mediated immunity, which operates alongside humoral immunity to defend the body against pathogens and abnormal cells.

Key players are CD8+ cytotoxic T cells and CD4+ helper T cells. Cytotoxic T cells recognize peptide antigens presented on MHC class I molecules on infected or malignant cells and can induce cell death through perforin and granzymes or via Fas-FasL interactions. Helper T cells, particularly Th1 cells, secrete cytokines such as interferon-gamma and IL-2 that activate macrophages and promote cytotoxic responses. Regulatory T cells help maintain self-tolerance and limit excessive responses.

Activation occurs when naive T cells are stimulated by antigen-presenting cells displaying peptide-MHC complexes, accompanied by co-stimulatory signals. Differentiation into effector subsets is driven by the cytokine milieu. The result is targeted elimination of infected or transformed cells and coordination of broader immune actions, including macrophage activation and support for other immune compartments.

Clinical relevance includes defense against intracellular pathogens (viruses, certain intracellular bacteria) and tumor surveillance. Tcellemediert is central to delayed-type hypersensitivity reactions, such as the tuberculin skin test, and is a focus of cancer immunotherapies that aim to enhance T cell responses, including checkpoint inhibitors and adoptive T cell transfer. Dysregulation can contribute to autoimmunity and graft rejection.

See also: immunology, T cells, cytotoxic T lymphocytes, MHC, delayed-type hypersensitivity.