What is the main function of the immune system?

The immune system's primary function is to defend against pathogens and diseases. It consists of a complex network of cells, tissues, and organs that work together to recognize and eliminate harmful invaders such as viruses, bacteria, parasites, and fungi. By identifying foreign substances, the immune system can mount an appropriate response, which may include the production of antibodies, activation of immune cells, and the coordination of inflammatory responses. This protective mechanism is crucial for maintaining health and preventing infections, as well as for recognizing and destroying cancerous cells.

In contrast, aiding in nutrient absorption relates more to the digestive system, while the transportation of gases in the blood is the job of the circulatory system. Regulating hormone levels falls under the endocrine system's function. Thus, the immune system's specific role in combating pathogens makes it distinctly important in maintaining overall health.