Key Difference – Immunoglobulin vs. Antibody
The production of antibodies is the key function of the human immune system. The antibody can identify and neutralize pathogens such as bacteria and viruses. Both immunoglobulin and antibody are substitutable terms. Some scientists believe that immunoglobulin as the main class of proteins that antibodies belong to based on their overall protein structure. This is the key difference between immunoglobulin and antibody. This article will elaborate on immunoglobulin and antibodies and highlight the difference between immunoglobulin and antibody.
What is Immunoglobulin?
The terms antibody and immunoglobulin are frequently used interchangeably. Antibodies belong to the immunoglobulin superfamily known as glycoproteins. However, based on the scientific evidence, an antibody is not identical to an immunoglobulin. B cells can synthesize two types of immunoglobulin, and they are a surface immunoglobulin, which are B-cell receptors and secreted immunoglobulin, which are antibodies.
What is Antibody?
An antibody is also identified as an immunoglobulin. This is a heavy, globular Y-shape protein created by plasma cells. It is used by the immune system to identify and neutralize pathogens such as bacteria and viruses. The antibody distinguishes an exclusive molecule of the harmful agent, known as an antigen, through the variable region. The creation of antibodies is the central function of the immune system, and they are secreted by immune system differentiated B cells known as plasma cells. It has been estimated that the human immune system produces about 10 billion diverse antibodies. They are capable of binding a unique epitope of an antigen. Furthermore, numerous complexes genetic mechanisms have developed which allow mammalian differentiated B cells to create a miscellaneous pool of antibodies from a comparatively small number of antibody genes.
What is the difference between Immunoglobulin and Antibody?
There are only a few differences between immunoglobulin and antibody that can be identified and they are;
Definition:
Immunoglobulin: A large group of glycoproteins that constitute the antibodies formed in response to antigenic stimuli.
Antibody: Immunoglobulin multichain glycoproteins synthesized by beta-cells and plasma cells in response to the introduction of foreign substances.
Classification:
Immunoglobulin: B cells produce two types of immunoglobulin such as surface immunoglobulin and secreted immunoglobulin.
Antibody: Antibodies are one of two classes of immunoglobulin.
Major Functions:
Immunoglobulin has two major functions. They are;
- Surface immunoglobulin: The membrane-bound form of an antibody may be known as a membrane immunoglobulin (mIg). It is a fragment of the B cell receptor (BCR), and it allows a B cell to identify when a specific antigen is existing in the body and stimulate B cell activation.
- Secreted immunoglobulin: Help to identify and destroy pathogens such as bacteria and viruses
Antibodies have one major function. The harmful agents are recognized and neutralized by antibodies. In addition to that, several immunodiagnostic procedures based on detection of complex antigen-antibody are utilized to identify and diagnose infectious diseases. For example ELISA, Western blot, immunofluorescence, immuno-diffusion, immuno-electrophoresis, and magnetic immunoassay.
Categorization
Immunoglobulin has five categories of antibodies. They are,
- IgA: most common form and they are present in mucous membranes of GI tract, respiratory tract, and in saliva and tears.
- IgD: It is present in serum, and its major function is involved in allergic responses
- IgE: It is present in the skin and mucous membranes, and it can respond to environmental antigens or foreign invaders. Therefore, it can play a role in skin epidemics.
- IgG: This is widespread throughout the body and main antibody defense against bacterial invasion and other antigens
- IgM: This is found in blood. They can fight blood infections and triggers IgG production.
Antibody: Different antibodies are produced by above immunoglobulin groups.
In conclusion, it is difficult to definitively state any major differences between immunoglobulin and antibodies. In simple terms, an antibody is produced against a given antigen (foreign substance or pathogenic organisms). The antibody produced by the B cells will exactly recognize the toxin or antigen and also create antigen-antibody complex. Thereby, antibody helps to neutralize the antigen from the body. In addition to that, the antibody produced by B cells will belong to the above Immunoglobulin(IgG) class.
References
Litman, G. W., Rast, J. P., Shamblott, M. J., Haire, R. N., Hulst, M., Roess, W., Litman, R. T., Hinds-Frey, K. R., Zilch, A., Amemiya, C. T. (1993). Phylogenetic diversification of immunoglobulin genes and the antibody repertoire.Mol. Biol. Evol.10 (1): 60–72.
Underdown, B. and Schiff, J. (1986). Immunoglobulin A: strategic defense initiative at the mucosal surface. Annu Rev Immunol, 4 (1): 389–417.
Milland, J. andSandrin, M. S. (2006).ABO blood group and related antigens, natural antibodies and transplantation.Tissue Antigens, 68 (6): 459–466.
Brehm-Stecher, B. and Johnson, E. (2004). Single-cell microbiology: tools, technologies, and applications. MicrobiolMolBiolRev,68(3): 538–559.
Image Courtesy:
1. “Mono-und-Polymere” by Martin Brändli (brandlee86) – Own work. [CC BY-SA 2.5] via Commons
2. Antibody svg By DigitalShuttermonkey (Recreated jpg originally uploaded by Muntasir Alam) [CC BY-SA 3.0], via Wikimedia Commons
