Putative adhesion molecule that mediates sialic-acid dependent binding to cells. Preferentially binds toalpha-2,3- and alpha-2,6-linked sialic acid. Also binds disialogangliosides (disialogalactosyl globoside, disialyllactotetraosylceramide and disialyl GalNAc lactotetraoslylceramide). The sialic acid recognition site may be masked bycis interactions with sialic acids on the same cell surface. In the immune response, may act as an inhibitory receptorupon ligand induced tyrosine phosphorylation by recruiting cytoplasmic phosphatase(s) via their SH2 domain(s) thatblock signal transduction through dephosphorylation of signaling molecules. Mediates inhibition of natural killercells cytotoxicity. May play a role in hemopoiesis. Inhibits differentiation of CD34+ cell precursors towardsmyelomonocytic cell lineage and proliferation of leukemic myeloid cells (in vitro)