CD1 molecules are non-polymorphic proteins that are structurally homologous to classical class I antigen presenting proteins (class Ia proteins) and bind beta-2-microglobulin. However, instead of presenting peptides in the binding groove, CD1 molecules bind glycolipids and present them to T cells (Batuwangala, T., D. Shepherd, S. D. Gadola, K. J. Gibson, N. R. Zaccai, A. R. Fersht, G. S. Besra, V. Cerundolo, and E. Y. Jones. J Immunol (2004) 172:2382. The crystal structure of human CD1b with a bound bacterial glycolipid). CD1 molecules are divided into two Groups, based on relatedness. Group 1 consists of the CD1a, CD1b, and CD1c molecules, which are expressed by most mammalian species except all muroid rodents, including mice. Group 2 consists of the CD1d molecule, which is expressed in mammals. CD1a-c present pathogen-specific lipid antigens to a diverse repertoire of T cells. The primary function known for CD1d molecules is to present glycolipids to NK T cells that express an invariant alpha chain (Va14-Ja18, or Va14i NKT cells in mice; Va24-Ja18 or Va24i in humans) (Hammond, K. J., and M. Kronenberg. Curr Opin Immunol (2003)15:683. Natural killer T cells: natural or unnatural regulators of autoimmunity?).
The NIH MHC Tetramer Core is currently supplying human CD1 a, b and c monomers and tetramers, and mouse and human CD1d monomers and tetramers produced using a lentivirus expression system. Investigators supply the ligands for the hCD1a-c molecules. However, CD1d reagents are available as empty monomers and tetramers or loaded with the ligands PBS57 and OCH. Both human and mouse CD1d reagents are generated with their species-matched b2m light chains.