What is the role of the immune system in the human body?

The immune system is responsible for defending the body against harmful invaders, such as bacteria, viruses, fungi, and parasites. It is made up of a network of cells, tissues, and organs, including white blood cells, lymph nodes, and antibodies. When the immune system detects a foreign pathogen, it activates various defenses, such as producing antibodies to neutralize the invader and activating specialized cells to destroy infected or damaged cells. The immune system also has a memory function, allowing it to respond more quickly if the same pathogen is encountered again.