The Complement System is one of the immune system’s most ancient, powerful, and elegant weapons. It’s a cascade of proteins in your blood plasma—think of it as the castle’s automated, booby-trap defense network.

The Biochemical Domino Effect

The name “complement” comes from the fact that it complements or works with antibodies. However, it can also be triggered on its own.

It works on a domino or fireworks fuse principle:

1. One protein activates.

2. It clips and activates the next.

3. That one clips and activates the next ten.

4. Those ten each activate ten more…

The result is a tiny initial signal explodes into a massive, localized attack.

The Three Pathways to Activation (Three Ways to Light the Fuse)

Imagine three different security systems that can all set off the same set of traps: