Final answer:
The complement system is a group of proteins that enhance the immune response by attacking and destroying pathogens in a cascading fashion.
Step-by-step explanation:
The complement system is a series of proteins constitutively found in the blood plasma. These proteins have a variety of functions in the innate immune response by attacking and destroying pathogens. The complement system consists of several proteins that enzymatically alter and fragment later proteins in a series, known as a cascade.
Once activated, the complement system marks pathogens for phagocytosis (opsonization) and creates pores in the pathogens' cell membranes to destroy them. It is termed as cascades because the series of reactions are irreversible and release fragments with these actions.