CD169

CD169, also known as sialoadhesin or siglec-1, is a type I transmembrane protein belonging to the sialic acid-binding immunoglobulin-like lectin (siglec) family. It is primarily expressed on macrophages and dendritic cells, particularly those residing in lymphoid tissues, spleen, and bone marrow. Its structure is characterized by an N-terminal V-set immunoglobulin domain followed by a stalk region containing multiple C2-set immunoglobulin domains. The extracellular portion of CD169 is responsible for binding to sialic acids, which are terminal sugar residues found on glycoproteins and glycolipids of other cells and pathogens.

The function of CD169 is multifaceted and heavily involved in immune responses. Its primary role is believed to be in mediating cell-cell adhesion and recognition through interactions with sialic acid-containing ligands. This interaction allows CD169-expressing cells to capture and present antigens, influencing the activation and differentiation of lymphocytes. CD169 has been implicated in the uptake of pathogens and immune complexes, contributing to innate immunity. Furthermore, its expression can be modulated by cytokines, suggesting its involvement in inflammatory processes and immune homeostasis. Research continues to explore the precise mechanisms by which CD169 contributes to immune surveillance, antigen presentation, and its potential therapeutic applications.