What does the immune system do regarding antigens it has previously encountered?

The immune system plays a crucial role in recognizing and responding to antigens, which are substances that can provoke an immune response. When the immune system encounters an antigen for the first time, it goes through a primary immune response, during which it generates specific immune cells and antibodies tailored to that antigen.

Following this initial encounter, the immune system retains a memory of the antigen through specialized memory cells, which include memory B cells and memory T cells. These memory cells enable the immune system to respond more rapidly and effectively if the same antigen is encountered again in the future. This process is known as immunological memory and is a foundational principle behind vaccinations, where exposure to a harmless form of an antigen can lead to long-lasting immunity.

As a result, when the immune system has previously encountered an antigen, it does not forget it. Instead, it is prepared to mount a quicker and stronger response upon subsequent exposures, making the option that highlights the immune system's ability to remember antigens for future responses accurately reflect the functionality of the adaptive immune system.