The immune response refers to the body's defense mechanism against foreign substances, such as bacteria or viruses. When a pathogen enters the body, it triggers an immune reaction that helps protect the body from infection and disease. This involves various components of the immune system, including white blood cells, antibodies, and chemical signals called cytokines. The immune response can be divided into two main categories: innate (the body's first line of defense) and adaptive (a more specific and targeted response). Overall, the immune response is a critical part of maintaining good health by defending against foreign invaders that could cause illness.