Immunology - Complement System C1 to C9

In Complement System, there are different types of proteins in the complement system. These proteins are named from C1 to C9.

Firstly, the antibody will bind onto the infectious particle. After that, C1 will attached onto the antibody.

After attaching onto the antibody, C1 will then be activated, and then it will split to form C2a and C4b fragments.

When these 2 fragments joined together, it will then form the C3 convertase.

C3 convertase is able to cleave C3 into C3a and C3b.

C3a is able to cleave C5 into C5a and C5b.

C5b, C6, C7, C8, and C9 are able to attach itself onto the infectious cell membrane, and therefore opening a hole on the membrane, and allowing the infectious cell content to lysate, and it leads to self-destruct. This process is known as MAC, which is known as Membrane Attacking Complex.

C3b is able to attach itself to the infectious cell, and therefore it will help in opsonisation, and it will then undergo phagocytosis.