How are memory B cells formed?

Memory B cell production is a key aspect of the adaptive immune system. The process by which memory B cells are formed involves multiple stages, starting with the first encounter with a new pathogen. 

1. On encountering a new antigen for the first time, naïve B cells with surface receptors that can bind to specific components of the antigen get activated. 
2. The activated naïve B cells undergo clonal expansion where they proliferate rapidly, producing a colony of identical cells. This takes place in the secondary lymphoid organ such as lymph nodes. 
3. Most of the activated B cells differentiate into plasma cells or effector B cells, which are responsible for producing antibodies that can eliminate the invading antigen and neutralize the infection.
4. A subset of the activated B cells differentiate into memory B cells. 

The notable feature of memory B cells is that they are capable of remembering the specific antigen that their naïve counterparts just encountered. In case of a subsequent encounter with the same antigen, memory B cells quickly differentiate into plasma cells, producing large quantities of antibodies to mount a faster and more effective immune response. Memory B cells can persist in the body for a very long time, sometimes for the person’s lifetime.