A Level Biology Practice Exam

What is the key characteristic of an autoimmune response?

1. It is always harmful.

2. It only occurs in plants.

3. It involves immune cells attacking pathogens.

4. It involves immune cells attacking the body’s own cells.

The correct answer is: It involves immune cells attacking the body’s own cells.

The key characteristic of an autoimmune response is that it involves immune cells attacking the body’s own cells. In a healthy immune system, the body is able to differentiate between foreign invaders, such as pathogens, and its own cells. However, in autoimmune responses, this distinction breaks down, leading to a misguided immune reaction where the body’s own tissues are mistakenly recognized as harmful. This can result in various autoimmune diseases, where the immune system targets its own organs and tissues, causing damage and dysfunction. The other options do not accurately define an autoimmune response. While the response can be harmful, it is not always harmful in a general sense as some immune responses are crucial for normal function and health. Autoimmune responses are not exclusive to plants; they primarily occur in animals, including humans. Lastly, although the immune system does indeed attack pathogens, this mechanism is characteristic of a healthy immune response, not an autoimmune one.