CD1b Long Isoform Extracellular Ligand-binding Domain (human, recombinant)

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.

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1. Moody, D.B., Zajonc, D.M., and Wilson, I.A. Anatomy of CD1-lipid antigen complexes. Nat. Rev. Immunol. 5(5), 387-399 (2005).

2. Dascher, C.C., Hiromatsu, K., Xiong, X., et al. Conservation of CD1 intracellular trafficking patterns between mammalian species. J. Immunol. 169(12), 6951-6958 (2002).

3. Briken, V., Jackman, R.M., Dasgupta, S., et al. Intracellular trafficking pathway of newly synthesized CD1b molecules. EMBO J. 21(4), 825-834 (2002).

4. Moody, D.B., and Suliman, S. CD1: From molecules to diseases. F1000Res. 6, 1909 (2017).

5. Shahine, A. The intricacies of self-lipid antigen presentation by CD1b. Mol. Immunol. 104, 27-36 (2018).

6. Strominger, J.L. An alternative path for antigen presentation: Group 1 CD1 proteins. J. Immunol. 184(7), 3303-3305 (2010).

7. Chancellor, A., Tocheva, A.S., Cave-Ayland, C., et al. CD1b-restricted GEM T cell responses are modulated by Mycobacterium tuberculosis mycolic acid meromycolate chains. Proc. Natl. Acad. Sci. USA 114(51), E10956-E10964 (2017).

8. Lee, C., Chen, L., Yu, C., et al. Prognostic value of CD1B in localised prostate cancer. Int. J. Environ. Res. Public Health 16(23), 4723 (2019).