Tcellemedieret

Tcellemedieret refers to immune responses that are primarily driven by T lymphocytes rather than antibodies. In immunology, this form of immunity is central to defenses against intracellular pathogens, virus-infected cells, and many tumor cells, and it operates alongside humoral (antibody-mediated) responses.

The mechanism begins with antigen presentation. T cells recognize peptide antigens displayed on major histocompatibility complex (MHC) molecules by antigen-presenting cells. Activation requires co-stimulatory signals and cytokines, after which naive T cells differentiate into effector and memory populations. Cytotoxic T cells (CD8+) directly kill infected or transformed cells through perforin and granzyme release or Fas–FasL interactions. Helper T cells (CD4+) orchestrate responses by secreting cytokines such as IFN-γ and IL-2, supporting macrophage activation and cytotoxic responses. Regulatory T cells (Tregs) help limit excessive reactions and maintain self-tolerance. Memory T cells provide faster responses upon re-exposure to the same antigen.

Types of Tcellemedieret responses include cell-mediated cytotoxicity, delayed-type hypersensitivity and broader T cell–driven regressive or protective immune actions. The effectiveness of Tcellemedieret immunity often depends on proper antigen presentation, receptor specificity, and the balance of cytokine signals.

Clinically, Tcellemedieret immunity is crucial in combating viral infections and many intracellular bacteria, as well as in tumor surveillance and graft rejection. Disorders may involve insufficient T cell responses, leading to infections or cancer, or excessive activation, contributing to autoimmune diseases. Vaccines and immunotherapies frequently aim to enhance or modulate T cell–mediated immunity.