Complement

**Semantic type:** Amino Acid, Peptide, or Protein|Immunologic Factor

**Definition:** The complement system is a complex system of serum proteins that interact in a cascade. Many of the early components are serine proteases that activate each other sequentially. This complement system consists of three separate activation triggers: (1) Ab binding to a cell surface, (2) formation of immune complexes, and (3) a carbohydrate component of a microbe's cell membrane. Along with this triggers, there are also two sets of mechanisms. Both of these mechanisms, classical pathway and alternative or properdin pathway, make MAC (Membrane Attack Complex), which can lyse and destroy the cell.