Memory B cells are a type of immune cell that play a crucial role in the body's defense against infections. After the body encounters a pathogen, such as a virus or bacteria, some B cells transform into memory B cells. These cells remain in the body for a long time, ready to respond quickly if the same pathogen is encountered again. When a memory B cell recognizes its specific pathogen, it can rapidly produce large amounts of antibodies. These antibodies help neutralize the pathogen, providing faster and more effective protection compared to the first immune response. This ability is the basis for long-lasting immunity, such as that achieved through vaccinations.