mouse monoclonal IgG2b; CD21 Antibody (A-3) is an IgG2b κ mouse monoclonal CD21 antibody (also designated CR2 antibody, Complement C3d Receptor 2 antibody, C3DR antibody, Epstein-Barr Virus Receptor antibody, Complement Receptor Type 2 antibody, EBV Receptor antibody, CD21 antibody, Complement C3d Receptor antibody, CD21 Antigen antibody, CVID7 antibody, SLEB9 antibody, or CR2 antibody) that detects the CD21 protein of mouse, rat and human origin by WB, IP, IF, IHC(P) and ELISA. CD21 Antibody (A-3) is available as both the non-conjugated anti-CD21 antibody form, as well as multiple conjugated forms of anti-CD21 antibody, including agarose, HRP, PE, FITC and multiple Alexa Fluor® conjugates. CD21 (also known as complement receptor (CR) type 2) is a type I integral membrane glycoprotein that serves as a receptor for the C3d complement fragment and for the Epstein-Barr virus. It plays a role in B cell activation and proliferation and undergoes phosphorylation after B cell activation with phorbol esters. CD21 is expressed on mature B cells, follicular dendritic cells, pharyngeal and cervical epithelial cells and a subset of thymocytes. The adaptive immune response is tightly regulated to limit responding cells in an antigen-specific manner. On B cells, co-receptors CD21/CD19 modulate the strength of B cell Ag receptor (BCR) signals, thereby influencing cell fate. CD21 is normally expressed during the immature and mature stages of B cell development. In association with CD19, CR21 plays an important role in enhancing mature B cell responses to foreign antigens.