Human Antigen-Presenting Glycoprotein CD1d (CD1D) Protein

Background

CD1D is a key member of the CD1 family of glycoproteins, which are specialized antigen-presenting molecules. CD1 proteins are distinct from classical major histocompatibility complex (MHC) class I and II molecules in that they present lipid and glycolipid antigens, rather than peptide antigens, to T cells. CD1D is unique within the CD1 family because of its specialized role in presenting lipid antigens to natural killer T (NKT) cells, particularly the invariant NKT (iNKT) cells, which express a semi-invariant T cell receptor (TCR). This interaction is essential for initiating rapid immune responses against a variety of pathogens, as well as in immune regulation. CD1D is expressed predominantly on antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells, but is also found on certain epithelial cells. Through its interaction with NKT cells, CD1D mediates a range of immune responses, including the production of cytokines that regulate the function of other immune cells, such as dendritic cells, natural killer (NK) cells, and conventional T cells. This makes CD1D important not only for pathogen defense but also for the regulation of inflammation, tolerance, and tumor immunity.