CD1d is a unique member of the group 2 CD1 molecules, structurally related to MHC class I proteins and forming a heterodimer with β-2-microglobulin. It is an antigen-presenting glycoprotein that binds and presents both self and microbial lipid and glycolipid antigens to T cells, particularly Natural Killer T （NKT） cells. CD1d is expressed on various cell types, including hematopoietic cells like macrophages, B cells, and dendritic cells, as well as non-hematopoietic cells such as intestinal epithelial cells. The protein is localized in the cell surface, endoplasmic reticulum, and lysosome. CD1d plays a crucial role in immune responses, including antigen processing and presentation via MHC class Ib, regulation of T cell proliferation, and cytokine production. It is also implicated in various diseases, such as pulmonary tuberculosis, autoimmune diseases, and certain cancers. Additionally, CD1d has been shown to have non-classical roles, such as modulating lipid metabolism in macrophages and providing protective effects in inflammatory bowel disease models.