Background：CD21 is a 145 kD transmembrane protein also known as complement C3d receptor （C3dR）, complement receptor 2 （CR2）, and Epstein-Barr virus receptor. CD21 is expressed on B cells, follicular dendritic cells, subsets of normal thymocytes and T cells, and some epithelial cells. CD21 is the receptor used by Epstein-Barr virus to infect B cells and is also the complement receptor for C3d. CD21 has also been shown to interact with a number of proteins, including CD23, CD19, annexin VI, CD81, iC3b, complement receptor 1 （CR1, CD35）, and interferon-alpha 1 （IFN-a1）.
仕様
Synonyms：Complement receptor type 2,CR2,Cr2,Complement C3d receptor,Epstein-Barr virus receptor,EBV receptor,CD21
