The monoclonal antibody 11H9 recognizes mouse complement component C3 and its activation products C3b, iC3b, C3d and C3dg. The complement system is an important part of the humoral response in innate immunity and consists of three different pathways. The third complement component C3 It is the classic of complement activation, replacement and the core of the lectin pathway. The activation product of the complement cascade contains new epitopes that do not exist in a single natural component. Complement factor C3 is composed of α-chain and β-chain.
The synthesis of C3 is tissue-specific and is regulated in response to a variety of stimulants. C3 is the most abundant protein in the complement system, and the serum protein level is about 1.3 mg/ml. Hereditary C3 deficiency makes people vulnerable to frequent attacks from bacterial infections. In ulcerative colitis and idiopathic chronic inflammatory bowel disease, the deposition of C3 in the diseased mucosa has been reported.
The proteolysis of certain enzymes causes the cleavage of C3 into C3a and C3b. C3b attaches to immune complexes and is further cleaved into iC3b, C3c, C3dg and C3f. The monoclonal antibody 11H9 recognizes intact C3 and its cleavage products C3b, iC3b, C3d and C3dg. These activation products are present in acute and chronic inflammatory diseases. Under chronic inflammatory conditions, the C3dg product is mainly located in the inflammation site recognized by the antibody 11H9 (C3c is cleared). The long-term processing/activation of C3 is at a low level, which will reduce the detection of C3 fragments C3b, iC3b and C3c.