What cells are responsible for memory in the immune system?

Memory B cells play a crucial role in the immune system's ability to remember past infections and respond more effectively upon re-exposure to the same pathogen. When B cells are activated by an antigen, they can differentiate into plasma cells, which produce antibodies, and also into memory B cells. These memory B cells remain in the body long after the initial infection has been cleared.

Upon subsequent encounters with the same antigen, memory B cells can rapidly proliferate and differentiate into plasma cells, leading to a swift and robust antibody response. This is essential for long-term immunity and is the principle behind vaccinations, which aim to create a pool of memory B cells against specific pathogens without causing disease.

Other cell types listed, such as plasma cells, helper T cells, and natural killer cells, serve different functions in the immune response but do not directly mediate immunological memory in the same way that memory B cells do. Plasma cells are primarily responsible for producing antibodies during an active immune response, helper T cells aid in orchestrating the immune response, and natural killer cells are involved in the innate immune response, targeting infected or cancerous cells rather than providing memory.