Which of the following is found in vaccines to evoke an immune response?

The correct answer is antigens, as they are the key components of vaccines designed specifically to provoke an immune response in the body. Antigens can be derived from pathogens, such as viruses or bacteria, and can be inactivated or attenuated forms (meaning they are killed or weakened) or subunits (specific parts of the pathogen, like proteins). Once introduced into the body through vaccination, these antigens stimulate the immune system to recognize them as foreign, prompting the production of antibodies and the activation of immune cells, ultimately leading to immunological memory. This prepares the immune system to respond more effectively in the event of future exposure to the actual pathogen.

In contrast, antibodies are the proteins produced by the immune system in response to antigens; they themselves are not components of vaccines intended to evoke an immune response. Macrophages are a type of immune cell that play a role in the immune response but are not found in vaccines. Similarly, B cells are the immune cells that produce antibodies in response to antigens; they are also not found in the vaccine itself. The function of vaccines relies on the introduction of antigens, which stimulates the body’s immune system and sets the stage for long-lasting immunity.