B Cells are a type of Lymphocytes that have an essential role in the Immune System.

The goal of B Cells are to make antibodies against antigens.

B Cells are formed in the Bone Marrow of mammals and often transferred to the Spleen.

The activity of this type of cell can be described as a “Humoral Immune Response”.

Memory B Cells are thus formed after an interaction by a foreign antigen reaction.

B Cells are important in the adaptive immune system

B Cells terminology comes from the “bursa of Fabricius” in birds

Another, but different type of immune response, is the Cell-Mediated Immune Response.

Cell-mediated immune response is largely controlled by T cells.

B Cells are quite different than T Cells.


Development of B Cells

Is a complex system of development and changing of the B cells

Occurs through several stages

Antibodies are essentially several chains and consist of 2 similar light chains, 2 similar heavy chains and genes that separate each antibody consists of a variable region and a constant region.

Within the V region, a process called VDJ recombination produces the variable portion of each B cell.

A receptor is found on each B cell called the B cell receptor (BCR).

If something goes wrong during development, that particle will be taken apart through apoptosis.


Function of B Cells

1.)  Immune security:

– B cells patrols the body in search of foreign or concerning particles

2.)  Immune encounter:

– B cell finds a foreign object.
– Becomes activated
– Can divide into either a plasma B cell or a memory B cell


B cell clones

– This means that in the beginning the B cells is alike the others

– They have the same components and antigens and clones are considered genetically identical to the same clones

– The number of clone types is amazing

– Clones are different from each other but are the same as well.

– Clones can each recognize a different antigen and once this occurs many cells of the same clone are produced.


B cells

Types of B cells

1.)  Memory B cells

– Are a class of B cells that divide after activation
– Activation occurs following an infection

Following the first or initial response to an antigen a colony of B cells are formed

– Most cells are plasma cells, but some become memory cells which endure a lifetime
– Memory cells remain after the infection has been resolved

Following the subsequent exposures to the same antigen

– Memory cells are already in place to protect and fight the current infection
– Additional clones will also respond to the 2nd attack
– More antigen protection will be produced

***  This is the principle behind vaccinations and booster doses


2.)  Plasma B Cells

– Are a group of B cells that divide after activation
– Following contact with a foreign antigen
– Production of large amount of antibodies are the goal of this group of cells
– Antibodies will help kill the foreign invader
– Antibodies will attach to the bacteria or virus and allow for the activation of the complement system and Phagocytosis
– Following the immune response, these cells are quickly destroyed


3.)  B-1 Cells

– Are another group of B cells
– Expresses a molecule called CD5
– Believed to allow B cell and another B cell to interact


4.)  B-2 Cells


5.)  Follicular B Cells

– Are another group of B cells
– Expresses large amount of IgM and IgD
– Expresses no CD5 and CD1


6.)  Marginal-Zone B Cells

–  Are another group of B cells
–  Can be quickly sent out from spleen and is often the first line of defense against blood-borne antigens

Activation of B Cells

–  Antigen is recognized by B-cells causes activation
–  Identification of “non-self” particles similar to T Cell can also cause activation


Problems with B cells

Certain autoimmune diseases may be a result of problems with B cells

Leukemia and Lymphoma are derived from abnormal B cells

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