Memory B cells have the longest lifespan among B-cell types. They are able to persist for years or even decades after an initial exposure to an antigen, providing rapid and robust immune responses upon re-exposure.
B cell receptors are membrane-bound antibodies that recognize antigens outside the cell, while T cell receptors recognize antigens on the surface of infected cells. B cell receptors are made of immunoglobulins composed of heavy and light chains, while T cell receptors are composed of alpha and beta chains or gamma and delta chains. B cell receptors can bind to soluble or membrane-bound antigens, while T cell receptors only recognize antigens presented by major histocompatibility complex molecules.