Complement proteins are a group of proteins found in the blood that play a crucial role in the immune system. They help the body fight infections by marking pathogens, such as bacteria and viruses, for destruction. When activated, these proteins can directly kill pathogens or enhance the ability of immune cells to eliminate them. The complement system consists of over 30 different proteins, which work together in a cascade-like manner. This system can be triggered by various factors, including the presence of pathogens or antibodies. Proper functioning of complement proteins is essential for maintaining a healthy immune response and preventing infections.