Mistry Anita R, O'Callaghan Chris A
Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford, UK.
Immunology. 2007 Aug;121(4):439-47. doi: 10.1111/j.1365-2567.2007.02652.x.
The outcome of an encounter between a cytotoxic cell and a potential target cell depends on the balance of signals from inhibitory and activating receptors. Natural Killer group 2D (NKG2D) has recently emerged as a major activating receptor on T lymphocytes and natural killer cells. In both humans and mice, multiple different genes encode ligands for NKG2D, and these ligands are non-classical major histocompatibility complex class I molecules. The NKG2D-ligand interaction triggers an activating signal in the cell expressing NKG2D and this promotes cytotoxic lysis of the cell expressing the ligand. Most normal tissues do not express ligands for NKG2D, but ligand expression has been documented in tumour and virus-infected cells, leading to lysis of these cells. Tight regulation of ligand expression is important. If there is inappropriate expression in normal tissues, this will favour autoimmune processes, whilst failure to up-regulate the ligands in pathological conditions would favour cancer development or dissemination of intracellular infection.
细胞毒性细胞与潜在靶细胞相遇的结果取决于抑制性受体和激活受体发出的信号平衡。自然杀伤细胞2D（NKG2D）最近已成为T淋巴细胞和自然杀伤细胞上的主要激活受体。在人类和小鼠中，多个不同基因编码NKG2D的配体，这些配体是非经典的主要组织相容性复合体I类分子。NKG2D-配体相互作用在表达NKG2D的细胞中触发激活信号，这促进了表达配体的细胞的细胞毒性裂解。大多数正常组织不表达NKG2D的配体，但在肿瘤细胞和病毒感染细胞中已记录到配体表达，从而导致这些细胞的裂解。配体表达的严格调控很重要。如果在正常组织中存在不适当的表达，这将有利于自身免疫过程，而在病理条件下未能上调配体则有利于癌症发展或细胞内感染的传播。
