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An antibody is a protein produced by the body's immune system when foreign objects are detected.The antibody recognises a specific site on the foreign target called antigens.

The antibody then binds to the antigens in order to remove them from the body. A wide range of substances are regarded as antigens, such as toxic materials like insect venom [1].

However, antibodies can also be produced when healthy tissue is mistaken for a harmful substance by the immune system. This is known as an autoimmune disorder [2].

Structure of Antibodies 

Antibodies are proteins composed of subunits of amino acids. The basis of the antibody molecule are four polypeptide chains, within which are two types, referred to as light and heavy chain. The light chain is around 25 kDa,and the heavy chain is 50 kDa. The heavy chain is important as the class of the antibody is derived from its structure. The way in which the two heavy chains are connected to one another is though disulfide bonds, they are then connected to a light chain by disulfide bonds as well. This therefore creates two identical antigen-binding sites.[3]

The regions of the heavy chain includes three constant domains, which are the same for all antibodies, and the one variable domain. The light chains are also composed of a constant domain and a variable domain. The variable regions of the antibodies are where the antigen binding site is located and the constant domain is responsible for the outcome of the antigen.[4] The Fc region is the part of the antibody that binds to cell surface receptors on cells such as macrophages. Finally, the Fab region is primarily known as the location for the antigen binding site. [5]


  1. The Editors of Encyclopaedia Britannica (2014) Antibody (last accessed 19/11/14)
  2. David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, and Stephanie Slon. (2012) Antibody. (last accessed 19/11/14)
  3. Janeway CA, Shlomchik MJ, Travers P, Walport M. Immunobiology: The Immune System in Health and Disease: 5th ed. New York, NY: Garland Science; 2001.
  4. Fanger M, Lydyard P, Whelan A. Immunology: 3rd ed. New York, NY: Garland Science; 2011.
  5. Novimmune. Antibodies [Internet]. Geneva, Switzerland; Novimmune SA; 2015 [cited 2015 Nov 20]. Available from:

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