Complement C3 is an inflammatory mediator in the body and is responsible for the immune response in the body. When viruses and bacteria infect the body, the body will stimulate an immune response to kill these pathogens, and C3 complement is one of the inflammatory mediators involved in the killing of bacteria and viruses. This is a normal physiological response and has a protective effect on the body. Of course, abnormal secretion of C3 complement can also lead to the development of diseases, such as C3 complement-associated nephropathy. For example, in lupus nephritis, if the C3 complement is significantly lower and the blood sedimentation is significantly higher, lupus is considered to be active. C3 complement can also assess the regression of the disease, for example, in acute glomerulonephritis, if C3 complement is found to gradually return to normal, it suggests that glomerulonephritis has recovered.