And the other protein that this can activate is the C Five, as we'll see in just a moment. So let's begin with the C Three. So here we have the inactive form of C Three that is moving around, circulating in the bloodstream. And eventually, once we form this, this complex activates this by cleaving it into C three B and C three A. So what exactly is the function of C three A? Well, C three A is a molecule known as an anaphylatoxin.