A Level Biology Practice Exam

What defines active immunity in the immune system?

1. It involves receiving antibodies from another source

2. It occurs when the body manufactures its own antibodies

3. It requires immediate response without prior exposure

4. It is dependent on memory cells only

The correct answer is: It occurs when the body manufactures its own antibodies

Active immunity is defined as the process in which an individual's immune system produces its own antibodies in response to an antigen. This can occur after an infection or through vaccination. When the body encounters a pathogen, it recognizes the foreign antigens present on that pathogen and activates the immune response, which includes the production of antibodies specifically tailored to target that pathogen. This process not only helps to eliminate the infection but also allows the immune system to build memory cells that can recognize the antigen if the individual is exposed to it again in the future. This long-term protection is a hallmark of active immunity and distinguishes it from passive immunity, where antibodies are obtained from another source, like maternal antibodies or antibody therapy. Therefore, the correct understanding of active immunity centers on the individual's ability to manufacture its own antibodies after exposure to an antigen.