noun, plural: memory B cells
A small, long-lived B lymphocyte that was previously exposed to a particular antigen, and then proliferates and produces large amounts of antibodies during re-exposure to the same antigen
B lymphocytes, also called B cells, are types of lymphocytes involved in the production of immunoglobulins, thus, in the humoral immune response of the adaptive immune system. There are many types of B lymphocytes (or B cells): plasma B cells, memory B cells, B-1 cells, B-2 cells, marginal-zone B cells, and regulatory B cells.
B cells come from the bone marrow. They are, then, released into the blood and the lymphatic system. B cell that encountered an antigen turns into an antigen-presenting cell. In the germinal centers of secondary lymphoid organs such as spleen and lymph nodes, the Helper T cell recognizes the signal (antigenic peptide) and activates the antigen-presenting B cell to proliferate. The clones that the parent B cell produces may differentiate into plasma cells or memory B cells.
A memory B cell is a dormant B cell. It is involved in the secondary immune response. It circulates throughout the body and produces more robust antibody-mediated immune response when exposed again to the same antigen (re-infection). Since the memory B cell is a clone, it would have the same B cell receptors (BCRs) as its parent B cell and therefore would be able to detect the same antigen.
A memory B cell is different from a plasma B cell in a way that it persists longer than a plasma cell.