CD1b is a member of the CD1 family of transmembrane glycoproteins and is an MHC class I-like molecule that presents lipid antigens to T cells.1 Alternative splicing of CD1B produces one full-length isoform, CD1b long, and one short isoform.2 CD1b long exists as a tetramer where each monomer is composed of a transmembrane CD1 heavy chain that contains three extracellular domains (α1-α3), which associate with β2-microglobulin to form a lipid-binding groove, as well as a cytoplasmic tail that contains a YXXZ endosomal sorting motif and interacts with the chaperone proteins AP-2 and AP-3 to direct CD1b intracellular trafficking.1,2,3,4 The CD1b short isoform lacks the endosomal sorting motif and is confined to the cell surface.2 CD1b expression is induced in antigen-presenting cells by bacteria or toll-like receptor 2 (TLR2), IL-1β, or GM-CSF stimulation and functions to present a variety of lipid antigens to T cells.5 CD1b is synthesized in the endoplasmic reticulum and is transported to the cell membrane where it expresses self-lipids, such as sphingolipids and phospholipids.5,6 It is then internalized and localizes to the late endosome or lysosome where it exchanges self-lipids for pathogen-derived lipids, including mycolates and lipoglycans, prior to being re-expressed on the cell surface for T cell presentation. CD1b protein levels are increased in skin lesions from patients with leprosy, in lung granulomas from patients with tuberculosis, and in postmortem-derived brain lesions from patients with multiple sclerosis.5,7 CD1B SNPs have been found in patients with prostate cancer.8 Cayman's CD1b Long Isoform Extracellular Ligand-binding Domain (human, recombinant) protein is a disulfide-linked homodimer. The reduced monomer, comprised of CD1b Long Isoform Extracellular Ligand-binding Domain (amino acids 18-303) fused to human IgG1 Fc at its C-terminus, consists of 527 amino acids, has a calculated molecular weight of 58.6 kDa, and a predicted N-terminus of Ser18. As a result of glycosylation, the monomer migrates at approximately 59 to 69 kDa by SDS-PAGE under reducing conditions.WARNING This product is not for human or veterinary use.
