Description: Leukocyte Ig-like receptors (LIRs) are a family of immunoreceptors expressed predominantly on monocytes and B cells and at lower levels on dendritic cells and natural killer (NK) cells. Activation of various immune cell types can be prevented by negative signaling receptors through interactions with specific ligands, such as MHC class I molecules by NK cells. All of the LIR inhibitory receptors, members of subfamily B, contain a cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM). Upon MHC class I (or other ligand) engagement and tyrosine phosphorylation of the ITIM, intracellular protein-tyrosine phosphatases such as SHP1 (PTPN6; MIM 176883) are recruited, and an inhibitory signal cascade ensues. Other LIR receptors, members of subfamily A, with short cytoplasmic regions containing no ITIMs and with transmembrane regions containing a charged arginine residue, may initiate stimulatory cascades (see, e.g., MIM 604810). One member of subfamily A (LILRA3; MIM 604818) lacks a transmembrane region and is presumed to be a soluble receptor.[supplied by OMIM]