CD21 FITC

The mouse monoclonal antibody produced by clone HB5 binds to complement receptor 2 (CR2), known as CD21, a 145 kDa glycoprotein of the complement control protein family. It is a receptor for the complement components C3d and C3g and, under pathological circumstances, for the Epstein-Barr virus (EBV). As complement breakdown fragments remain bound to the agent initiating the complement activation in the first place, CD21 plays an important role in the uptake of immunocomplexes. In addition, it plays a role in B cell development and activation as well as memory B cell survival. Thus, it is a key component in developing and maintaining humoral immune response to T-dependent antigens. CD21 associates with CD19, CD81 and the B cell receptor. The cell surface marker CD21 is expressed on mature B cells and follicular dendritic cells. It is used as a cell marker for the phenotyping of leukemias.