Strategies for target cell recognition by natural killer cells

Area of Science:

• Immunology
• Cellular Biology
• Molecular Recognition

Background:

• Natural killer (NK) cell activity is governed by a delicate equilibrium of inhibitory and stimulatory receptors.
• The precise interactions between stimulatory receptors and their corresponding ligands remain incompletely elucidated.
• NKG2D, a key stimulatory receptor, is expressed across various immune cells including NK cells, activated CD8+ T cells, gammadelta T cells, and macrophages.

Purpose of the Study:

• To investigate the poorly understood interactions of stimulatory receptors, particularly NKG2D, with their ligands.
• To define the cellular ligands recognized by the NKG2D receptor.
• To explore the potential of NKG2D-ligand interactions as a novel mechanism for immune system target cell recognition.

Main Methods:

• Identification and characterization of cellular ligands for the NKG2D receptor.
• Analysis of ligand expression patterns in different cellular contexts, including transformed and infected cells.
• Comparative studies in both murine and human systems.

Main Results:

• Four distinct families of NKG2D ligands have been identified in mice and humans.
• These ligands share distant structural homology with MHC class I molecules.
• Certain NKG2D ligands are significantly upregulated on transformed and infected cells, signaling these cells for immune system engagement.

Conclusions:

• The identification of NKG2D ligands provides crucial insights into NK cell activation pathways.
• Upregulation of these ligands on stressed cells suggests an 'induced-self' recognition mechanism.
• NKG2D-mediated recognition of 'induced-self' ligands may represent a fundamental new strategy for immune surveillance and target cell elimination.