C3a and C3d Peptides
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Introduction
The third component of complement (C3) is the core of the complement system, which was discovered in 1912 when Ritg treated serum with snake venom. C3 convertase acts on amino acids 77-78 of the complement C3 molecule and cleaves it into C3a and C3b. C3a peptide is an allergen that triggers inflammatory responses which mediated by complement. C3a peptide is an anaphylatoxin molecule produced by the activation of the replenishment system. In mammals, C3a is thought to be an endogenous signal that induces an inflammatory response and is also an inducer that activates several key innate immune processes. C3b peptide is an opsonin that enhances the phagocytosis ability of phagocytic cells. C3b peptide is an important opiner (op2 sonin) that binds bacteria or other particles quickly and binds to receptors on the surface of neutrophils, mononuclear or macrophages, promoting the phagocytosis of pathogens. Both C3a and C3b play important roles in both the classical and alternative pathways of complement activation.
Mechanism of action
C3 molecules, including C3a and C3b, have numerous binding sites with other molecules, which are the molecular basis for the biological activity of complement. C3aR is receptor of C3a peptide. In mammals, C3aR is the only seven-transmembrane member of the rhodopsin family. C3aR is mainly found in lymphocytes and granulocytes in the blood. C3b binds to complement type I receptor (CR1, CD35) abundantly present on red blood cells, neutrophils, monocytes and macrophages via the CR1 binding site. This mainly mediates the clearance of antigen-antibody complexes and promotes phagocytosis of phagocytic cells.
Application of C3a and C3d Peptides
It has been reported that the determination of serum complement C3a and C3b levels can help determine the potential activity of systemic lupus erythematosus and guide the rational use of corticosteroids. Plasma complement C3 and C3/C3b values in patients with chronic hepatitis B are important parameters for judging the severity of hepatitis. C3a and C3b peptides are associated with a variety of effector cells, play an immunomodulatory role, and are widely used in clinical testing and vaccine preparation. They are important for the diagnosis and prevention of diseases.
Reference
- Lambris, J.D., Reid, K.B., Volanakis, J.E. (1999) The evolution ,structure ,biology and pathophysiology of complement. Immunol Today, 20 (5): 207-211.
