Cutting edge: Human myelomonocytic cells express an inhibitory receptor for classical and nonclassical MHC class I-molecules

Leukocyte activation can be negatively regulated by inhibitory receptors specific for MHC class I-molecules. While one inhibitory receptor Hg-like transcript 2 (ILT2), is expressed by all lymphoid and myelomonocytic cell types, other receptors display a more selective tissue distribution. Here we characterize an inhibitory receptor termed ILT4, which is selectively expressed in monocytes, macrophages and dendritic cells (DCs), binds classical class molecules and the nonclassical class I molecules HLA-G, and transduces negative signals that can inhibit early signaling events triggered by stimulatory receptors. ILT4 may control inflammatory responses and cytotoxicity mediated by myelomonocytic cells and may modulate their Ag presenting functions, focusing immune responses to microbial challenges and avoiding autoreactivity.