Memory B cells recognize a pathogen during a primary encounter and survive in the body for long periods. If the body encounters the same pathogen again, these cells react immediately, resulting in a stronger and faster secondary immune response. Many vaccines utilize this property by introducing weakened or dead pathogens to stimulate memory B cell production, allowing the immune system to rapidly recognize and neutralize future infections.

State University of New York at Buffalo

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B lymphocytes, which are commonly called B cells, express surface B cell receptors for antigen immunoglobulins.  B cells are further differentiated based on which kinds of antigens they respond to and which type of antibodies they produce. There are two different types of B cells:
1. Plasma B cells
2. Memory B cells

B Lymphocytes

Memory B cells are created after several rounds of proliferation, and additional cytokines provided by the TH2 cells stimulate the differentiation of activated B cell clones into memory B cells. They respond quickly to subsequent exposures to the same protein epitope.

Memory B Cell

Plasma B cells produce antibodies (also called immunoglobulins) that bind to the antigens which makes it easier for phagocytic cells to target and kill them. There are five classes of immunoglobulins:
1. IgG
2. IgM
3.IgA
4. IgE
5. IgD

Function of Plasma B cells

- Antigens (foreign substance) stimulate creation of preexisting B cell the antibodies which recognize the antigen. 
- The genes that code for antibodies are limited – so where does the diversity come from? 
- The antibody diversity is accounted from the genetic changes of the B lymphocytes development. 
- Antibodies are coded by DNA segments: V, J and C for the light chains and V, D, J and C for the heavy chains. Because there are so many segments and many versions of these segments are possible, the possibilities for antibodies are significantly large. 
- Additionally, changes occur once a B cell has encourntered an antigen and secrets antibodies. 
- The B cells divide and the antibody gene mutation increases and creates a trial of nucleotides that vary (one amino acid mutations for every cell generation) and this allows for antigen specificity of the antibody to be fine tuned over many cell generations. This antigen-binding affinity increases with the B cell proliferation. 


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