Clone 1A5 recognizes the CD170 antigen, a single-pass transmembrane protein member of the immunoglobulin superfamily, also known as sialic acid-binding Ig-like lectin 5 (siglec-5). CD170 is expressed on neutrophils, monocytes, dendritic cells, and subsets of tissue macrophages. It contains two tyrosine-based motifs in its cytoplasmic tail implicating signaling functions and forms a 140 kDa dimer on the cell surface. Tyrosine phosphorylation of CD170 leads to recruitment of the tyrosine phosphatases SHP-1 and SHP-2, which in turn efficiently inhibits FcεRI-mediated calcium fluxing and serotonin release. CD170 binds α 2-3– and α 2-6–linked sialic acid as well as glycophorin A, and is involved in cell adhesion.