A Level Biology Practice Exam

What are secondary defences in the immune system responsible for?

1. Preventing pathogens from entering the body

2. Attacking pathogens that have entered the body

3. Producing antibodies before exposure to pathogens

4. Inhibiting the reproduction of pathogens

The correct answer is: Attacking pathogens that have entered the body

The secondary defences in the immune system are primarily responsible for attacking pathogens that have already entered the body. Once a pathogen breaches the body's initial barriers, such as the skin and mucosal surfaces, the secondary immune response is activated. This involves the actions of various immune cells, including lymphocytes (B cells and T cells) and phagocytes, which work together to identify, target, and eliminate the invading pathogens. B cells produce specific antibodies that bind to the pathogens, marking them for destruction and neutralizing their effects. T cells can directly kill infected cells or help orchestrate the overall immune response. Additionally, phagocytes, like macrophages and neutrophils, engulf and digest the pathogens, effectively removing them from the body. These secondary defences are essential for providing a robust response to infections and are different from the primary defences, which are focused on prevention rather than response. The immune memory established through secondary responses allows for a quicker and more effective attack if the same pathogen is encountered again in the future.