What are B cell receptors & how they come about?
As mentioned before, B cells produce antibodies. However, they do not produce those antibodies until they become fully activated. Each and every B cells has a unique receptor protein called the B cell receptor (BCR) on its surface that will specifically bind to antigen molecules. The BCR is also known as immunoglobulin (Ig) and it differentiates B cells from other types of lymphocytes as well as being the main protein involved in B cell activation. B cell receptors may be bound to the B cell membrane known as surface immunoglobulins or secreted as antibodies (Ab). The secreted antibodies carry out humoral immunity.
When the B cell receptor binds to antigen, it initiates a signal through two proteins (Ig-alpha and Ig-beta) non-covalently in the B cell receptor complex. The signal initiated by binding of antigen to the B cell receptor complex causes growth and proliferation of the B cell. This will then lead to the creation of an amplified clone of effector cells that secrete the antigen-specific immunoglobulin. In addition, activating the B cell receptor by antigen will also result in the production of memory cells that persist in circulation to produce a more rapid immune response after future challenges by the same antigen.
In case all of you are wondering how does a B cell receptor looks like.
Here is the structure.
• 4 polypeptide chains
• 2 identical heavy (H) chains and 2 identical light (L) chains
• The polypeptide chains are joined together by interchain disulfide bonds.
References
http://www.biocarta.com/pathfiles/h_bcrmolecule.asp
http://www.newworldencyclopedia.org/entry/B_cell
http://people.rit.edu/gtfsbi/imm/parhamimages.htm/Chapter%2002/figure%2002-23.jpg
http://www.immunecentral.com/immune-system/iss15.cfm
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