Recombinant Mouse CD83 Fc Chimera Protein, CF

Mouse CD83 is a 30 - 35 kDa member of the Siglec (or sialic-acid-binding immunoglobulin-like lectin) family of transmembrane proteins (1, 2, 3). CD83 is synthesized as a type I transmembrane glycoprotein that contains a 114 amino acid (aa) extracellular region, a 22 aa transmembrane segment, and a 39 aa cytoplasmic domain. It contains one V type Ig-like domain in the extracellular region with no inhibitory cytoplasmic motif(s). In the extracellular region, mouse and human CD83 are 66% aa identical (1, 2, 4). Relative to mouse, human CD83 has an 11 aa insertion in its extracellular domain and is expressed as a 45 - 55 kDa protein (1, 4, 5, 6). No alternate splice variants have been reported for mouse. In human, however, one soluble splice form has been reported and proteolytic processing is suggested to generate a second circulating isoform (6, 7). Notably, although soluble CD83 has the potential to exist as either a monomer or disulfide-linked dimer, both show immunosuppressive activity (4, 8, 9). Membrane CD83, by contrast, is immunostimulatory (10). CD83 is a primary marker for dendritic cells (3, 5, 6). It is also found on B cells (6, 11), neutrophils (12), monocytes and macrophages (13). Except for dendritic cells, CD83 expression is often transient. CD83 binds to sialic acids on monocytes (3). The function of CD83 is only now becoming clear. As noted, membrane-immobilized CD83 appears to promote T cell proliferation, particularly of CD8⁺ cytotoxic T cells (14). On monocytes, CD83 may also drive monocytes into a fibrocyte phenotype (14). And a lack of membrane-expressed CD83 leads to an unusual IL-4/IL-10 producing CD4⁺ T cell phenotype (15).