Cytotoxic T cells.
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. Obviously, the activity of such a potent cell is tightly regulated. Indeed, a predominance of stimulatory over inhibitory signals is required for effective immune responses to pathogens, and a predominance of inhibitory over stimulatory signals is required for maintenance of self-tolerance. Still, several situations occur in which an inappropriate CTL response leads to either autoimmune disease or persistence of pathogens.
Andersen
Mads Hald
MH
Tumor Immunology Group, Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
Schrama
David
D
Thor Straten
Per
P
Becker
Jürgen C
JC
D001327:Autoimmune Diseases / Q000276:immunology; D015415:Biomarkers / Q000032:analysis; D003602:Cytotoxicity, Immunologic; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000276:immunology; D007157:Immunologic Surveillance; D008213:Lymphocyte Activation; D009369:Neoplasms / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D015415:Biomarkers; D011948:Receptors, Antigen, T-Cell