A healthy immune system depends on an adequate supply of proteins that bind to and neutralize harmful invaders. what are these proteins known as?

A healthy immune system depends on an adequate supply of proteins that bind to and neutralize harmful invaders. These proteins are known as complements and are composed of 25% plasma proteins. The complements are inactive, unless there is an invader. Invaders activate the protein and PTH (parathyroid hormone) is created between the invader and the protein.