Clone REA197 recognizes the mouse CD169 antigen, a Single-pass type I membrane protein also known as Sialoadhesin or Sialic acid-binding Ig-like lectin 1 (Siglec-1). CD169 is a macrophage-restricted cell surface receptor that mediates sialic-acid dependent binding to lymphocytes, including granulocytes, monocytes, natural killer cells, B-cells and CD8+
T-cells. It is a member of the sialic acid-binding IgG-like lectin (Siglec) family of proteins characterized by affinity to specifically sialylated ligands, and under normal conditions is expressed on subsets of macrophages in secondary lymphoid tissues, such as lymph node and spleen. However, CD169+
macrophages can also be found in a variety of pathological conditions, including (autoimmune) inflammatory infiltrates and tumors. CD169 has been shown to contribute to sialylated pathogen uptake, antigen presentation and lymphocyte proliferation, and to influence both immunity and tolerance. Additionally, CD169 positive macrophages, along with mesenchymal stem cells and β-adrenergic neurons, form the hematopoietic stem cell niche in the bone marrow. CD169+
macrophages mediate signaling between the various cells and seem to promote hematopoietic stem cell retention to the niche.