The 7-239 monoclonal antibody specifically binds to Sialic acid-binding Ig-like lectin 1 (Siglec-1), which is also known as Sialoadhesin (SN), or CD169. Siglec-1 is a type I transmembrane glycoprotein that belongs to the Siglec family within the Ig superfamily. This adhesion molecule especially binds to glycolipids and glycoproteins with terminal α-2 sialyl residues. Siglec-1 is expressed by macrophages and dendritic cells and serves as a cellular interaction molecule. Its expression can be upregulated by cells in response to type II collagen, or to cytokines including interferons, and tumor necrosis factor. Siglec-1 plays roles in endocytosis, hematopoiesis, and leucocyte migration. It mediates macrophage binding to various cell types including developing and mature leucocytes. Siglec-1 that is expressed by dendritic cells can also bind HIV-1 and may mediate viral transfer to bystander CD4+ T cells. Several Siglec-1 counter-receptors have been described including CD43, CD206, and CD227 which are expressed by T cells, macrophages, or breast cancer cells, respectively. The 7-239 antibody reportedly blocks Siglec-1 functions in some cellular assay systems.
The antibody was conjugated to BD Horizon™ BUV496 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.