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B Cells

B Cells are a type of Lymphocytes that have an essential role in the Immune System. The goal of this type of cell is to make antibodies against antigens.

They 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. They are important in the adaptive immune system and the 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:

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

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 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 interaction between cells

4.)  B-2 Cells

5.)  Follicular B Cells

–  Are another group of similar 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