Anti-Complement C3b/iC3b/C3dg Antibody, clone 1H8 clone 1H8, from mouse

Complement C3 (UniProt P01024; also known as C3 and PZP-like alpha-2-macroglobulin domain-containing protein 1) is encoded by the C3 (also known as CPAMD1) gene (Gene ID 718) in human. C3 is initially translated with an N-terminal 22-amino acid signal peptide sequence, which is then removed to produce the 1641-amino acid mature C3. It plays a central role in the activation of complement system. Its activation is required for the activation of both classical and alternative pathway of complement (CPC and APC, respectively). C3 is cleaved into C3a and C3b during CPC activation by the C3-convertase C4b2a composed of the activated C4 and C2. In APC, C3 is cleaved by the C3-convertase C3bBb composed C3b and the activated form of factor B (Bb). C3b serves as an opsonizing agent, and can be further cleaved by Factor I into C3c and C3d. iC3b is a proteolytically inactive C3b fragment that still opsonizes target microbes or cells, but cannot further amplify/activate the complement cascade through APC. iC3b can be further cleaved to C3dg, and finally to C3d. Unregulated activation of APC can result in paroxysmal nocturnal hemoglobinuria (PNH) that is characterized by chronic intravascular hemolysis. Clinical C5-neutralizing mAb treatment prevents the formation of cytolytic membrane attack complex (MAC) of complement, but does not block APC activation. Consequently, PNH patients are left with immune-mediated hemolytic anemia and their erythrocytes become opsonized with complement C3. Monoclonal antibodies (mAbs) against C3b/iC3b are useful for monitoring and studying C3b/iC3b deposit on PNH blood cells and mAbs with neutralizing activities are useful tools for studying C3-mediated CPC and APC.