A Level Biology Practice Exam

The long-term immune response is primarily mediated by B memory cells. These cells are a type of lymphocyte that are generated following the initial exposure to an antigen. Once formed, B memory cells persist in the body for years or even decades after the initial infection has been cleared. They allow for a faster and more robust response if the same antigen is encountered again in the future. This characteristic makes them crucial for providing long-lasting immunity, such as that seen with vaccinations and natural infections.

In contrast, B effector cells and plasma cells are primarily involved in the immediate immune response. B effector cells differentiate into plasma cells that produce antibodies specific to the antigen, but they do not have the long-term persistence that memory cells do. Macrophages play a significant role in the immune system by phagocytosing pathogens and presenting antigens, but they do not contribute specifically to long-term immunity in the same way that memory cells do.