May act as receptor. Negatively regulates TCR-mediated CD4(+) T cell proliferation and activation, possibly by binding an unknown ligand on the T cell surface. Enhances Toll-like receptor-mediated production of pro-inflammatory cytokines by macrophages and neutrophils. Interacts with Fc receptor gamma chain FCER1G. Expressed in lung, uterus, lymph nodes, spleen, thymus and bone marrow. Expressed in bone marrow CD11b(+)Gr-1(+) granulocyte precursors and mature neutrophils. Up-regulated in CD11b(+)Ly6G(+) and CD11b(+)Ly6C(+) neutrophils upon S.typhimurium bacterial infection. Up-regulated in CD11b(+)Ly6C(intermediate)Ly6G(high)MHCI(-) neutrophils and CD11b(+)Ly6C(high)Ly6G(low)MHCII(+) inflammatory monocytes in response to TLR4 ligand lipopolysaccharide (LPS) stimulation. Up-regulated in cultured macrophages and dendritic cells by TLR4 ligand LPS, TLR2-TLR6 ligand MALP-2 (a bacterial lipopeptide from M.fermentans), TLR1-TLR2 ligand Pam3CSK4 (a synthetic bacterial lipopeptide), TLR3 ligand polyinosinic:polycytidylic acid (poly(I:C), a double-stranded RNA synthetic analog) and TLR7 synthetic ligand imiquimod (R-837). N-glycosylated.