6.5　Cytotoxic T Lymphocyte

The immune system is a complex arrangement of cells and molecules that preserve the integrity of the organism by elimination of all elements judged dangerous.Within the immune system, a humoral and a cellular as well as an innate and an adaptive arm can be differentiated.The key players of adaptive cellular immune responses are T lymphocytes in general and, for the effector function, cytotoxic T lymphocytes (CTLs) in particular.T lymphocytes arise in the bone marrow and migrate to the thymus for maturation.During this process, T cells somatically rearrange gene segments, eventually leading to the expression of a unique antigen-binding molecule, the T-cell receptor (TCR).This receptor allows them to monitor all cells of the body, ready to destroy any cell posing a threat to the organism.Cytotoxicity is exerted directly through the Fas or perforin pathway and/or indirectly by the release of cytokines [128].(https://www.daowen.com)