CD83 is a single-transmembrane protein with a calculated molecular weight (MW) of 23 kDa, but due to heavy and differential glycosylation, its apparent MW ranges from 23 to 70 kDa. CD83 is predominantly expressed on mature dendritic cells (DCs) and has been used as a DC activation/maturation marker as its increased expression is correlated with upregulation of HLA class II antigen expression on DCs. CD83 is also expressed at a low level on lymphocytes and is upregulated upon lymphocyte activation. Thymic epithelial cells also express CD83, which is required for normal CD4+ T cell development. CD83 is also expressed as a soluble form (sCD83) that can be found in serum of healthy adults. sCD83 has been shown to negatively regulate immune response by lymphocytes.
