Which immunity is developed through the injection of an antigen, such as a flu shot?

The concept being tested here revolves around how immunity is obtained. The correct answer, active acquired immunity, refers to the protection that develops in response to an exposure to an antigen, which can occur through vaccination or after an infection. When you receive a flu shot, you are being exposed to a weakened or inactivated version of the flu virus, which serves as the antigen that prompts your immune system to generate a response. This process involves the creation of antibodies and memory cells that will help the body recognize and fight off the actual virus in the future.

Active acquired immunity is long-lasting because the antibodies and memory cells created will remain in the body, allowing for a quicker and more effective response if the body encounters the real virus later. This distinguishes it from passive acquired immunity, which involves receiving antibodies from another source, such as a mother to her baby through breast milk, and generally provides a short-term defense.

Natural immunity occurs when a person contracts and recovers from a disease, and innate immunity refers to the natural defenses present in the body that provide a first line of defense against pathogens. Each of these other types of immunity plays a role in the overall immune response but does not fit the scenario of receiving an injection of an antigen like a flu shot.