The primary role of the immune system in humans is to protect the body from infectious agents and diseases. It achieves this through a complex network of cells, tissues, and organs that work together to identify and eliminate pathogens, such as bacteria, viruses, and parasites. The immune system distinguishes between self and non-self cells, launching immune responses to attack foreign invaders while maintaining tolerance to the body's own cells. This defense mechanism is essential for overall health and plays a critical role in recovering from illnesses.