Putative adhesion molecule that mediates sialic-acid dependent binding to cells. The sialic acid recognition site may be masked by cis interactions with sialic acids on the same cell surface. In the immune response, may act as an inhibitory receptor upon ligand induced tyrosine phosphorylation by recruiting cytoplasmic phosphatase(s) via their SH2 domain(s) that block signal transduction through dephosphorylation of signaling molecules. Homodimer; disulfide-linked. Interacts with PTPN6/SHP-1 and PTPN11/SHP-2 upon phosphorylation. Expressed by monocytic/myeloid lineage cells. Found at higher levels in spleen, liver and heart. Found at lower levels in kidney and lung. Contains 1 copy 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. Phosphorylation of Tyr-432 is required for binding to PTPN6 and PTPN11. Phosphorylation of Tyr-455 is involved in binding to PTPN6. Tyr-432 needs to be phosphorylated prior to Tyr-455. Belongs to the immunoglobulin superfamily. SIGLEC (sialic acid binding Ig-like lectin) family. Siglec-E