[Pathogen/Antigen] === C3d ---> Binds to CR2 (CD21) on B Cell | v Binds to Surface IgM (BCR) ---> Dual Signaling Lowering Activation Threshold
: Upon installation, you will see two icons. Choose the one that matches the measurement units (meters vs. feet) used in your region. 2. Core Learning Path [Pathogen/Antigen] === C3d ---> Binds to CR2 (CD21)
This simultaneous cross-linking clusters the CD19/CD21/CD81 co-receptor complex. This process lowers the B-cell activation threshold by up to 10,000-fold. It accelerates affinity maturation, B-cell memory development, and high-titer antibody synthesis. Biomedical Applications of C3d Complement C3d enables cell-mediated immunity ... - PNAS It accelerates affinity maturation
Unlike its transient precursor fragments, C3d possesses an exceptionally long tissue-residence time. It features an amino acid structure that exposes a binding site for complement receptor 2 (CR2/CD21). This receptor is expressed heavily on B lymphocytes and follicular dendritic cells. The Mechanism of a Natural Molecular Adjuvant B-cell memory development