Memory B cells are a type of immune cell that are responsible for mounting a rapid and effective immune response upon re-exposure to a previously encountered antigen. These cells are generated during an initial immune response to an antigen, such as a pathogen or vaccine, and are able to "remember" that antigen and quickly produce antibodies specific to it upon a subsequent encounter. Memory B cells play a critical role in the long-term protection against pathogens and are important for the development of immunity to specific infections. Researchers study memory B cells to better understand how the immune system responds to infections and vaccines, and to develop strategies for enhancing the immune response to these threats.