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Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells.. A cytotoxic T cell (also known as T C, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8 + T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens such as viruses or bacteria, or ...
These cells are defined by the expression of the CD8 protein on their cell surface. Cytotoxic T cells recognize their targets by binding to short peptides (8-11 amino acids in length) associated with MHC class I molecules, present on the surface of all nucleated cells. Cytotoxic T cells also produce the key cytokines IL-2 and IFNγ.
Cellular immunity protects the body through: T-cell mediated immunity or T-cell immunity: activating antigen-specific cytotoxic T cells that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
CTLs are able to eliminate most cells in the body since most nucleated cells express class I MHC molecules. The CTL-mediated immune system can be divided into two phases. In the first phase, functional effector CTLs are generated from naive T c cells through activation and differentiation. In the second phase, affector CTLs destroy target cells ...
Once mature, T cells emigrate from the thymus to provide vital functions in the immune system. [11] [12] Each T cell has a distinct T cell receptor, suited to a specific substance, called an antigen. [12] Most T cell receptors bind to the major histocompatibility complex on cells of the body.
Antigen presentation stimulates immature T cells to become either mature "cytotoxic" CD8+ cells or mature "helper" CD4+ cells. An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation.
In contrast to cytotoxic T lymphocytes, natural killer (NK) cells are normally inactivated upon recognizing MHC I molecules on the surface of cells. Therefore, in the absence of MHC I molecules, NK cells are activated and recognize the cell as aberrant, suggesting that it may be infected by viruses attempting to evade immune destruction.
Antigen presentation is a vital immune process that is essential for T cell immune response triggering. Because T cells recognize only fragmented antigens displayed on cell surfaces, antigen processing must occur before the antigen fragment can be recognized by a T-cell receptor.