What is the function of the immune system?

The immune system's primary function is to protect the body against infections and diseases caused by pathogens, such as bacteria, viruses, fungi, and parasites. It achieves this through a complex network of cells, tissues, and organs that work together to identify and eliminate these harmful invaders. The immune system includes components like white blood cells, which play a critical role in detecting and responding to pathogens. When an infection occurs, these immune cells coordinate a response that may involve the production of antibodies, activation of different immune cells, and the initiation of inflammatory processes to contain and destroy the threat.

In contrast, other options do not relate to the immune system's primary role. For example, the function of transporting gases in the blood is the responsibility of the circulatory system, primarily through red blood cells. Metabolism regulation is a function associated with the endocrine system and involves hormones that control various metabolic processes. Additionally, muscle contractions are controlled by the muscular and nervous systems, which manage movement and coordination. Each system in the body has specific responsibilities, and the immune system's dedicated task of defending against pathogens highlights its critical importance in maintaining health and homeostasis.