Description: The monoclonal antibody eBio4E3 reacts with an eptiope shared by mouse CD21 (CR2) and CD35 (CR1). CD21 and CD35 are alternatively spliced transcripts from the Cr2 gene, which result in cell-surface proteins of 145 and 190 kDa, respectively. CD21 and CD35 are expressed by mature B cells, but not on thymocytes, peripheral T cells, erythrocytes or platelets. Furthermore, there is little evidence which demonstrates their expression on macrophages. CD21 is a receptor for complement component C3d and Epstein-Barr virus (EBV), and in association with CD19 and CD81, CD21 also participates in B-cell activation through the B cell receptor. Cr2 deficient mice display impaired inflammatory and humoral immune responses in vivo. The anti-mouse CD21/35 monoclonal antibody clones eBio4E3 and eBio8D9 do not cross-block each other suggesting that they bind to different epitopes.