Complement is a part of the immune system that helps the body fight foreign invaders. It is an important part of the body's defense system and is made up of proteins that circulate in the bloodstream and are activated when a pathogen is present in the body. The proteins work in different ways, including coating the foreign invader and marking it for destruction, lysing infected cells, and releasing inflammatory chemicals to attract other immune cells.

Complement is a complex set of proteins that are part of the human body’s immune system. These proteins are circulating in the bloodstream, and can be activated when a pathogen is present. Complement is important for helping the body to fight off foreign invaders, such as viruses, bacteria, fungi and parasites.

Complement can be activated by a number of triggers. These include antibodies that are made by the body in response to an infection; bacterial enzymes that can react with proteins in the complement system; and certain particle receptors in the surface of cells which may detect a foreign molecule. Once activated, the proteins in the complement system can perform several functions, including coating and targeting the surface of foreign invaders, lysing infected cells, and releasing inflammatory chemicals to attract other immune cells.

Complement proteins can also help to remove parts of the body that are not functioning, such as bacteria or old red blood cells. In this way, it helps to maintain the normal healthy functioning of the body. Complement is also involved in allergic reactions and some autoimmune diseases, in which it can become overly active and cause damage to healthy cells and tissues. In some cases, a lack of complement activity may also be seen, as in some infections, such as HIV/AIDS.

In conclusion, complement is an important part of the body’s defense system, helping to identify and destroy foreign invaders, and to maintain an optimal state of health. It is a complex system made up of proteins that are activated when a pathogen is present, and which can perform a variety of functions to help fight off the invader. However, it can cause harm when it is overly-active or not functioning properly. It is therefore important to ensure that the levels of complement in the body remain balanced.