Classical Pathway

Classical Pathway

Classical Pathway

The classical pathway, which consists of three components, C I, C4 and C2,is activated by the immune complexes of antigen and by 19G and 19M antibodies. The immune complex is designated by EA. E is the antigen (erythrocyte in the original work) and A is the antibody. It should be emphasized that other antigens can substitute E. In fact any antigen that can complex with an antibody has the potential. The C components bind to EA to form a very large macromolecular complex written as EAC142356789. Note that component C4 attaches to the complex out of numerical order.

The first component of C, C1 contains a calcium ion and three polypeptides, C1q, C1r, and C1s. C1q binds to the Fc portion of the antibody of the E-A immune complex. Binding of C1q leads to rearrangement of the structure in C1r and C1s. C1s acquires an enzyme activity and becomes an esterase (C1a). EAC1a is the first complex containing an activated complement component. C1a converts native and C2 into activated states. Activated C4 binds to. EAC1a to from EAC1a, 4. C2 binds (in presence of MgH) to activated C4 forming EACa1, 4, 2. (:4)2 has the descriptive name C3 convertase, which splits C3 into C3a and C3b. C3b binds to the complex to from EACla,4,2,3b.

Home | Site map | Submit Article | Directory | Search