Cellular ligands of activating NK receptors

Trends Immunol. 2005 Apr;26(4):221-6. doi: 10.1016/j.it.2005.02.007.


Human natural killer (NK) cells are equipped with a series of surface receptors that recognise different cellular ligands on potential target cells. Some of these ligands [e.g. human leukocyte antigen (HLA) class I] prevent an NK-mediated attack by interacting with inhibitory NK receptors (e.g. killer Ig-like receptors). Other ligands interact with activating NK receptors that, once engaged, induce both cytotoxicity and lymphokine release. Tumour transformation (or viral infection) frequently results in downregulation of surface HLA class I molecules together with upregulation or de novo expression of ligands of triggering NK receptors. Thus, transformed cells can become highly susceptible to NK-mediated lysis. However, although NK cells use different means to identify and fight target cells, target cells have various strategies to hide themselves, and disarm or even confuse the immune system.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Antigens, Differentiation, T-Lymphocyte / metabolism
  • Histocompatibility Antigens Class I / metabolism
  • Humans
  • Killer Cells, Natural / immunology*
  • Ligands
  • Models, Immunological
  • Neoplasms / immunology
  • Receptors, Immunologic / metabolism*
  • Receptors, Natural Killer Cell


  • Antigens, Differentiation, T-Lymphocyte
  • CD226 antigen
  • Histocompatibility Antigens Class I
  • Ligands
  • Receptors, Immunologic
  • Receptors, Natural Killer Cell