CD21, also known as CR2, C3d receptor and EBV receptor), is expressed strongly on mature B cells, follicular dentritic cells and weakly on immature thymocytes and T lymphocytes. In B-cell ontogeny, CD21 appears after the pre-B-stage, is maintained during peripheral B-cell development and is lost upon terminal differentiation into plasma cells. CD21 expression is also gradually lost after stimulation of B cells in vitro. CD21 functions as receptor for C3d, C3dg and iC3b Complement components, for EBV and for IFNalpha. CD21 binds to CD23 and associates with CD19, CD81 and Leu13 to form a large signal-transduction complex involved in B cell activation.
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Protein Aliases: complement C3d receptor; complement receptor type 1; complement receptor type 2; EBV receptor; epstein-Barr virus receptor; expressed in B lymphocytes
Gene Aliases: C3DR; CD21; CD35; Cr-1; Cr-2; Cr1
Entrez Gene ID: (Mouse) 12902