These cells are a type of lymphocytes that are essential in the the immune system.
Typical activity is similar to a humoral immune response.
This type of response is somewhat different than cell-mediated immune response.
Cell-mediated immune response is largely controlled by T cells
B cells are quite different and their goal is to make antibodies against antigens.
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
B cells are formed in the bone marrow of mammals and often transferred to the spleen
Development
Is a complex system of development and changing of the B cells
Occurs through several stages
Antibodies are esentially 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.
Types of B cells
1.) Memory B cells
2.) Plasma B cells
3.) B-1 cells
4.) B-2 cells
5.) Follicular B cells
6.) Marginal-zone B cells
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
Plasam 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
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
B-2 cells
Follicular B cells
- Are another group of B cells
- Expresses large amount of IgM and IgD
- Expresses no CD5 and CD1
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
- Antigen is recognized by B-cells causes activation
- Indentification 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