Recombinant Mouse CD1d1 Fc Chimera Protein, CF

CD1d is a 48 kDa transmembrane glycoprotein that belongs to the CD1 family of glycolipid antigen-presenting MHC-like molecules. In mouse, there are two closely related CD1d genes, CD1d1 and CD1d2, whereas human and rat have only one (1, 2). Mature mouse CD1d1 consists of a 284 amino acid (aa) extracellular domain (ECD) with one Ig-like domain, a 21 aa transmembrane segment, and a 10 aa cytoplasmic tail (3). Within the ECD, mouse CD1d1 shares 94% aa sequence identity with mouse CD1d2, and 65% and 87% with human and rat CD1d, respectively. Complexes of CD1d1 with beta 2-microglobulin and endogenous glycolipids are constitutively expressed on antigen presenting cells, cortical thymocytes, liver sinusoidal endothelial cells, Kupffer cells, and hepatocytes (1). A cytoplasmic motif mediates CD1d1 recycling through the endosomal/lysosomal system where it is loaded with processed exogenous glycolipids by saposin lipid transfer proteins (4 - 8). CD1d1-presented glycolipids are recognized by canonical NKT cells that utilize an invariant V alpha 14-J alpha 18 chain in their T cell receptor (V alpha 24-J alpha 18 in human) (9, 10). NKT cells that express V chains other than  alpha 14 can also recognize CD1d1-presented glycolipids but do not require them to be endosomally loaded (10, 11). NKT cells respond to a variety of CD1d1-presented glycolipids including alpha -galactosylceramide ( alpha -GalCer), a structural relative of microbial cell wall components, and the endogenous isoglobotrihexosylceramide (iGb3) (2, 9, 12). The interaction with glycolipid-loaded CD1d1 is critical for NKT cell development and induces their rapid secretion of both Th1 and Th2 type cytokines (10, 11, 13, 14). In humans, infection with HSV-1 suppresses NKT cell activation by blocking the intracellular cycling of CD1d in antigen presenting cells (15).