{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"CD21, also known as CR2, complement component (3d/Epstein Barr virus) receptor 2, is an integral membrane glycoprotein of molecular weight 140 kDa, involved in the complement system. CD21 binds to C3d. B-cells have CR2 receptors on their surfaces, allowing the complement system to play a role in B-cell activation and\n maturation. Complement component receptor-2 (CR2) is the membrane protein on B-lymphocytes to which the Epstein-Barr virus (EBV) binds during infection of these cells."}]},{"type":"paragraph","children":[{"type":"text","value":"Anti-CD21 is useful in the identification of follicular dendritic cell matrixes found in normal lymph nodes and tonsillar tissue. This antibody also labels Follicular Dendritic Cell Tumor/Sarcomas. The antigen is absent on T-lymphocytes, monocytes, and granulocytes."}]}]}