How does the immune system maintain human health

1. Identify and remove foreign invasive antigens, such as pathogenic microorganisms. This function of preventing the invasion of external pathogens and removing invasive pathogens and other harmful substances is called immune defense.

2. Identify and eliminate mutated tumor cells, aging cells, dead cells or other harmful components in the body. This function of finding and eliminating "non-self" components in the body at any time is called immune surveillance.

3. Maintain the internal stability of the immune system through autoimmune tolerance and immune regulation. (This function is called autoimmune stabilization. )