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Immunoglobulin Y (abbreviated as IgY) is a type of immunoglobulin which is the major antibody in bird, reptile, and lungfish blood. It is also found in high concentrations in chicken egg yolk. As with the other immunoglobulins, IgY is a class of proteins which are formed by the immune system in reaction to certain foreign substances, and specifically recognize them. IgY is often mislabelled as Immunoglobulin G (IgG) in older literature, and sometimes even in commercial product catalogues, due to its functional similarity to mammalian IgG and Immunoglobulin E (IgE). However, this older nomenclature is obsolete, since IgY differs both structurally and functionally from mammalian IgG,〔Larsson A, Bålöw RM, Lindahl TL, Forsberg PO. Poult Sci. 1993 Oct;72(10):1807-12.Chicken antibodies: taking advantage of evolution--a review.〕 and does not cross-react with antibodies raised against mammalian IgG.〔(Structure, Function and Physicochemical Properties of IgY ), Gallus Immunotech. Accessed 28 October 2010.〕 Since chickens can lay eggs almost every day, and the yolk of an immunised hen's egg contains a high concentration of IgY, chickens are gradually becoming popular as a source of customised antibodies for research. (Usually, mammals such as rabbits or goats are injected with the antigen of interest by the researcher or a contract laboratory.)〔REVIEW - Chicken Antibodies- IgY - http://www.oramune.com/custom.aspx?id=7〕 Ducks produce a truncated form of IgY which is missing part of the Fc region. As a result, it cannot bind complement or be picked up by macrophages. This may be one reason ducks are less easily killed by avian influenza compared to chickens, but can still become infected and spread the virus easily. IgY has also been analyzed in the Chinese soft-shelled turtle, ''Pelodiscus sinensis''.〔Zhen Xu, Gai L Wang, P Nie. Mol Immunol. 2009 vol. 46 (10) pp. 2124-32. IgM, IgD and IgY and their expression pattern in the Chinese soft-shelled turtle Pelodiscus sinensis.〕 ==Characteristics== In chickens, immunoglobulin Y is the functional equivalent to Immunoglobulin G (IgG). Like IgG, it is composed of two light and two heavy chains. Structurally, these two types of immunoglobulin differ primarily in the heavy chains, which in IgY have a molecular mass of about 65,100 atomic mass units (amu), and are thus larger than in IgG. The light chains in IgY, with a molar mass of about 18,700 amu, are somewhat smaller than the light chains in IgG. The molar mass of IgY thus amounts to about 167,000 amu. The steric flexibility of the IgY molecule is less than that of IgG. Functionally, IgY is partially comparable to Immunoglobulin E (IgE), as well as to IgG. However, in contrast to IgG, IgY does not bind to Protein A, to Protein G, or to cellular Fc receptors. Furthermore, IgY does not activate the complement system. The name ''Immunoglobulin Y'' was suggested in 1969 by G.A. Leslie and L.W. Clem, after they were able to show differences between the immunoglobulins found in chicken eggs, and immunoglobulin G. Other synonymous names are ''Chicken IgG'', ''Egg Yolk IgG'', and ''7S-IgG''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Immunoglobulin Y」の詳細全文を読む スポンサード リンク
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