CD1d

CD1d is a nonclassical major histocompatibility complex class I-like molecule that presents endogenous and exogenous lipid antigens to CD1d-restricted T cells, particularly natural killer T (NKT) cells, thereby linking innate and adaptive immunity through rapid cytokine-mediated immune regulation^[1][2]. Mechanistically, CD1d-dependent antigen presentation controls the activation of invariant NKT (iNKT) and type II NKT cell subsets, which recognize structurally diverse glycolipids and coordinate downstream responses involving dendritic cells, NK cells, B cells, and conventional T lymphocytes^[3][4]. In mucosal tissues and other immune compartments, CD1d-mediated lipid sensing contributes to host defense, inflammatory regulation, and tissue immune homeostasis through specialized lipid antigen presentation pathways^[2][5]. In disease models, CD1d-restricted NKT cells participate in antimicrobial immunity, tumor surveillance, autoimmunity, and inflammatory disorders, making the CD1d axis a widely used experimental platform for studying immune modulation and disease pathogenesis^[3][6]. Compared with group 1 CD1 isoforms that primarily present lipid antigens to distinct T-cell populations, CD1d is the only group 2 CD1 molecule and exhibits a specialized functional relationship with NKT-cell activation and immune regulation^[2]. In mice, the homologous proteins CD1d1 and CD1d2 display distinct biological roles, with evidence indicating differential contributions to NKT-cell development and function despite structural similarity^[7]. For experimental applications, the glycolipid agonist α-galactosylceramide (α-GalCer) remains a prototypical CD1d ligand that robustly activates iNKT cells and is extensively used to investigate antitumor immunity and CD1d-dependent immunotherapeutic strategies^[3][4].