Immunoglobulin Y

Immunoglobulin Y abbreviated IgY is a class of immunoglobulin molecules that are contained in the sera of chickens and, at high concentrations, especially in the yolk of hen's eggs. As with the other immunoglobulins are also in IgY proteins that are made by the immune system in response to certain foreign structures and specifically recognize this.

Properties

Immunoglobulin Y is the functional equivalent of chicken IgG, and as this made ​​up of two light and two heavy chains constructed. Structurally, both immunoglobulin classes differ mainly in the heavy chains with IgY have a molecular weight of about 65.1 kilodaltons and thus are larger than for IgG. The light chains of IgY are having a molecular weight of about 18.7 kilodaltons somewhat smaller in comparison to IgG. The molar mass of IgY amounts to about 167 kilodaltons. The steric flexibility of the IgY molecule is less than that of IgG.

Functionally similar IgY both partially with IgE as well as IgG. However IgY does not bind to protein A or cellular protein G and not to Fc receptors, in contrast to IgG. In addition, IgY does not activate the complement system. The name of immunoglobulin Y was in 1969 by G. A. Leslie and L.W. Clem suggested, after they were able to show differences between immunoglobulins and immunoglobulin G found in chicken eggs. Other synonymous names are Chicken IgG, Egg Yolk IgG or 7S IgG.

Bioanalytical applications

For the targeted production of antibodies and their use in the field of bioanalytics IgY has several advantages over the use of mammalian antibodies. Since the antibodies are obtained from the yolk of eggs laid, there is a non-invasive method of antibody production. The animals therefore no blood for collection of blood serum must be removed. The repeated oviposition by the same hen the available quantity of a particular antibody increases significantly. The cross-reactivity with mammalian proteins is much lower than that of IgG. In addition, the immune response directed against certain antigens in chickens is more pronounced than in rabbits or other mammals. Because of the emerging during the immune response immunoglobulins IgY is only found in chicken eggs, no impurities with IgA or IgM are in corresponding preparations contain. The yield of IgY from a chicken egg is similar to the of IgG from rabbit serum.

A disadvantage of IgY as compared to mammalian antibodies is that the purification of the egg yolk is more difficult than that of IgG from the blood serum. This is in large part due to the fact that IgY can not be bound by protein A and protein G. So it may be other components of the sample, for example, other proteins, can not be separated by means of these two substances. In addition, before using the rich existing lipids and lipoproteins of the yolk must be removed. Antibody -containing blood sera, however, can directly partially, without complicated purification steps are used in bioanalysis.

Application in food

IgY is used especially in Asian countries like Japan as a component of food. So there yogurt products are sold as containing specific IgY. This prevents the attachment of bacteria of the genus Helicobacter pylori in the stomach. The IgY used for this purpose is obtained from the eggs of immunized chickens. Antibodies are produced against salmonella and other bacteria, but also against viruses and used as part of the diet to protect against these pathogens.