Cedarlane’s anti-Human CD21 monoclonal antibody specifically binds human CD21, also known as Complement component (3d/Epstein Barr virus) receptor 2 (CR2). CD21 is a protein expressed on mature B cells and follicular dendritic cells, and is weakly expressed on immature thymocytes and T lymphocytes. CD21 binds to C3d, C3dg, and iC3b in the complement system. Other ligands include Epstein Barr virus and Interferon alpha. CD21 plays a role in B cell activation by binding to CD23 and forming a co-receptor complex with CD19, CD81, and Leu13.