The immune system is an important system for biological entities to carry out immune responses and immune functions. It consists of immune organs, immune cells, and immune molecules.
The immune system has the ability to recognize and eliminate antigenic foreign substances, to coordinate with other systems within the body, and to maintain the stability of the internal environment and physiological balance. The immune system is the most effective weapon against pathogens' invasion, capable of detecting and clearing foreign substances, and extrinsic microorganisms that cause fluctuations in the internal environment.
If the human body were seen as a country, the immune system would be the army that maintains national security. Once there's an invasion from enemies or an internal rebellion, the army would quickly detect the enemies or rebels and deploy to eliminate them.
