Receptor for class I MHC antigens. Recognizes a broad spectrum of HLA-A, HLA-B, HLA-C, HLA-G and HLA-F alleles (PubMed:11169396, PubMed:12853576, PubMed:16455647, PubMed:20448110, PubMed:27859042). Involved in the down-regulation of the immune response and the development of tolerance. Recognizes HLA-G in complex with B2M/beta-2 microglobulin and a nonamer self-peptide (peptide-bound HLA-G-B2M) triggering differentiation of type 1 regulatory T cells and myeloid-derived suppressor cells, both of which actively maintain maternal-fetal tolerance (PubMed:20448110, PubMed:27859042, PubMed:16455647). Competes with CD8A for binding to class I MHC antigens. Inhibits FCGR1A-mediated phosphorylation of cellular proteins and mobilization of intracellular calcium ions (PubMed:11875462, PubMed:12853576, PubMed:9548455, PubMed:9842885). Binds PTPN6 when phosphorylated. Binds FCGR1A. Interacts with peptide-bound HLA-G-B2M; this interaction is direct (PubMed:16455647). Interacts with peptide-bound HLA-F-B2M; this interaction is direct (PubMed:11169396). Expressed in monocytes and at lower levels in myeloid and plasmacytoid dendritic cells. Expressed in tolerogenic IL10-producing dendritic cells (PubMed:20448110). Expressed in myeloid-derived suppressor cells during pregnancy (PubMed:27859042). Detected at low levels in natural killer (NK) cells. Expressed in B cells. Induced on monocyte-derived macrophages by S.typhimurium infection. Contains 3 copies of a cytoplasmic motif that is referred to as the immunoreceptor tyrosine-based inhibitor motif (ITIM). This motif is involved in modulation of cellular responses. The phosphorylated ITIM motif can bind the SH2 domain of several SH2-containing phosphatases. Phosphorylated on tyrosine residues. Dephosphorylated by PTPN6. Alternative use of an acceptor site.