Natural killer (NK) cells attack tumor and infected cells, but the receptors
and ligands that stimulate them are poorly understood. Here we report the
expression cloning of two murine ligands for the lectin-like receptor NKG2D.
The two ligands, H-60 and Rae1, are distant relatives of major histocompatibility
complex class I molecules. NKG2D ligands are not expressed by most normal
cells but are up-regulated on numerous tumor cells. We show that mouse NKG2D
is expressed by NK cells, activated CD8+ T cells and activated
macrophages. Expression of either NKG2D ligand by target cells triggers NK
cell cytotoxicity and interferon- secretion by NK cells, as well as
nitric oxide release and tumor necrosis factor transcription by macrophages.
Thus, through their interaction with NKG2D, H-60 and Rae1 are newly
identified potent stimulators of innate immunity.
, are distant relatives of major histocompatibility
complex class I molecules. NKG2D ligands are not expressed by most normal
cells but are up-regulated on numerous tumor cells. We show that mouse NKG2D
is expressed by NK cells, activated CD8+ T cells and activated
macrophages. Expression of either NKG2D ligand by target cells triggers NK
cell cytotoxicity and interferon-
secretion by NK cells, as well as
nitric oxide release and tumor necrosis factor 
transcription by macrophages.
Thus, through their interaction with NKG2D, H-60 and Rae1
