The 440c monoclonal antibody specifically recognizes Siglec-H, a type I transmembrane glycoprotein that is encoded by Siglech (Sialic acid binding Ig-like lectin H). Siglec-H contains two immunoglobulin domains in its extracellular region and a cytoplasmic domain that lacks tyrosine-based signaling motifs unlike other CD33-related Siglec-like molecules. Siglec-H is expressed on progenitors of plasmacytoid dendritic cells (pDCs) and depends on DAP12 for cell surface expression and intracellular signaling function. In addition to its expression on pDC, Siglec-H may also be expressed by splenic marginal zone macrophages, medullary macrophages in lymph nodes, and microglia. Siglec-H may regulate the production of type I interferons (IFN-I) by pDCs and other cell types. There is no clear human ortholog for mouse Siglec-H.
The antibody was conjugated to BD Horizon Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.