Monoclonal antibody ELBE-1 recognizes human CD83. CD83 is a cell surface marker predominantlyexpressed on mature DCs. Expression has been found on circulating and tissue DCs. Additionally CD83is found on activated B and T lymphocytes. Human CD83 is composed of 205 amino acids but has, dueto extensive glycosylation, a molecular weight of ca 45 kDa. CD83 is expressed as a conserved anoncovalently associated single chain molecule membrane protein. CD83 is considered a marker forfully matured dendritic cells in the peripheral circulation. An essential role has not been found. However,its function primarily lies in the regulation of T- and B-cell maturation and the regulation of theirperipheral responses. CD83 is supposed to function as a co-stimulator for T-cell activation similar toCD80 or CD86. Enhanced expression on DCs correlates with their T cell activating capacity. Besidesthe membrane version of the protein also a soluble form occurs (sCD83). sCD83 levels are raised insera from patients of chronic lymphocytic leukemia and other haematological malignant diseases andin the synovial fluid of rheumatoid arthritis. While the membrane bound form has immune stimulatorycapacity, the soluble form has the opposite effect and is considered to have immunosuppressivepotential. Due to its inhibitory functions, sCD83 has potential for treatment of eg. autoimmune diseasesand transplantation.In contradiction to most clones, antibody ELBE-1 is besides flow cytometry applicable in western blottingand ELISA (detecting of sCD83). ELBE-1 recognizes a linear epitope and doesn’t influence T cellactivation.