Immunoglobulin Y
Encyclopedia
Immunoglobulin Y 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 However, this older nomenclature is obsolete, since IgY differs both structurally and functionally from mammalian IgG, and does not cross-react with antibodies raised against mammalian IgG.
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.)
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.
(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.
and their application in bioanalysis
. Since the antibodies are extracted from the yolks of laid eggs, the method of antibody production is non-invasive. Thus, no blood must be taken from the animals for the extraction of blood serum.
The available quantity of a given antibody is considerably increased through repeated egg laying from the same hen. The cross-reactivity
of IgY with proteins from mammals
is also markedly less than that of IgG. Furthermore, the immune response against certain antigens
in chickens is more strongly expressed than in rabbits
or other mammals
.
Of the immunoglobulins arising during the immune response, only IgY is found in chicken eggs. Thus, in preparations from chicken eggs, there is no contamination with Immunoglobulin A
(IgA) or Immunoglobulin M
(IgM). The yield of IgY from a chicken egg is comparable to that of IgG from rabbit serum.
One disadvantage of IgY, as compared to mammalian antibodies, is that the isolation of IgY from egg yolk is more difficult than the isolation of IgG from blood serum. This is due in large part to the fact that IgY cannot be bound with Protein A
and Protein G
. Thus, it cannot be separated from other components of the assay, for example from other proteins. Additionally, the egg yolk's rich store of lipids
and lipoproteins
must be removed. Antibody-containing blood serums, on the other hand, can sometimes be directly used in bioanalysis, i.e., without complicated isolation steps.
countries, IgY is used as an ingredient in foods. Thus, for example, yoghurt
products are distributed, which contain specific IgY. This hinders the attachment of bacterial
species
Helicobacter pylori
in the stomach
. The IgY used for this purpose is extracted from the eggs of immunized hens. Antibodies against Salmonella
and other bacteria, as well as against viruses
, are produced in this manner, and employed as a nutritional component for protection against these pathogens
.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
, reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
, and lungfish
Lungfish
Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed...
blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. It is also found in high concentrations in chicken egg yolk. As with the other immunoglobulins, IgY is a class of proteins
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
which are formed by the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
in reaction to certain foreign substances, and specifically recognize them.
IgY is often mislabelled as Immunoglobulin G
Immunoglobulin G
Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...
(IgG) in older literature, and sometimes even in commercial product catalogues, due to its functional similarity to mammalian IgG and Immunoglobulin E
Immunoglobulin E
Immunoglobulin E is a class of antibody that has been found only in mammals. IgE is a monomeric antibody with 4 Ig-like domains...
(IgE). However, this older nomenclature is obsolete, since IgY differs both structurally and functionally from mammalian IgG, and does not cross-react with antibodies raised against mammalian IgG.
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
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
of interest by the researcher or a contract laboratory.)
Ducks produce a truncated form of IgY which is missing part of the Fc region. As a result, it cannot bind complement
Complement
In many different fields, the complement of X is something that together with X makes a complete whole—something that supplies what X lacks.Complement may refer to:...
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.
Characteristics
In chickens, immunoglobulin Y is the functional equivalent to Immunoglobulin GImmunoglobulin G
Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...
(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
Molecular mass
The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...
of about 65,100 atomic mass units (amu), and are thus larger than in IgG. The light chains in IgY, with a molar mass
Molar mass
Molar mass, symbol M, is a physical property of a given substance , namely its mass per amount of substance. The base SI unit for mass is the kilogram and that for amount of substance is the mole. Thus, the derived unit for molar mass is kg/mol...
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
Immunoglobulin E
Immunoglobulin E is a class of antibody that has been found only in mammals. IgE is a monomeric antibody with 4 Ig-like domains...
(IgE), as well as to IgG. However, in contrast to IgG, IgY does not bind to Protein A
Protein A
Protein A is a 40-60 kDa MSCRAMM surface protein originally found in the cell wall of the bacterium Staphylococcus aureus. It is encoded by the spa gene and its regulation is controlled by DNA topology, cellular osmolarity, and a two-component system called ArlS-ArlR. It has found use in...
, to Protein G
Protein G
Protein G is an immunoglobulin-binding protein expressed in group C and G Streptococcal bacteria much like Protein A but with differing specificities. It is a 65-kDa and a 58 kDa cell surface protein that has found application in purifying antibodies through its binding to the Fc region...
, or to cellular Fc receptors
Fc receptor
An Fc receptor is a protein found on the surface of certain cells - including natural killer cells, macrophages, neutrophils, and mast cells - that contribute to the protective functions of the immune system....
. Furthermore, IgY does not activate the complement system
Complement system
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
. 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.
Bioanalytic Applications
As compared to mammalian antibodies, IgY offers various advantages for the targeted extraction of antibodiesAntibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
and their application in bioanalysis
Bioanalysis
Bioanalysis is a sub-discipline of analytical chemistry covering the quantitative measurement of xenobiotics and biotics in biological systems.-Modern bioanalytical chemistry:Many scientific endeavors are dependent upon...
. Since the antibodies are extracted from the yolks of laid eggs, the method of antibody production is non-invasive. Thus, no blood must be taken from the animals for the extraction of blood serum.
The available quantity of a given antibody is considerably increased through repeated egg laying from the same hen. The cross-reactivity
Cross-reactivity
Cross-reactivity is the reaction between an antibody and an antigen that differs from the immunogen. It is sometimes also referred to as crossimmunity or cross-protective immunity...
of IgY with proteins from mammals
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
is also markedly less than that of IgG. Furthermore, the immune response against certain antigens
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
in chickens is more strongly expressed than in rabbits
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
or other mammals
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
.
Of the immunoglobulins arising during the immune response, only IgY is found in chicken eggs. Thus, in preparations from chicken eggs, there is no contamination with Immunoglobulin A
Immunoglobulin A
Immunoglobulin A is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day....
(IgA) or Immunoglobulin M
Immunoglobulin M
Immunoglobulin M, or IgM for short, is a basic antibody that is produced by B cells. It is the primary antibody against A and B antigens on red blood cells. IgM is by far the physically largest antibody in the human circulatory system...
(IgM). The yield of IgY from a chicken egg is comparable to that of IgG from rabbit serum.
One disadvantage of IgY, as compared to mammalian antibodies, is that the isolation of IgY from egg yolk is more difficult than the isolation of IgG from blood serum. This is due in large part to the fact that IgY cannot be bound with Protein A
Protein A
Protein A is a 40-60 kDa MSCRAMM surface protein originally found in the cell wall of the bacterium Staphylococcus aureus. It is encoded by the spa gene and its regulation is controlled by DNA topology, cellular osmolarity, and a two-component system called ArlS-ArlR. It has found use in...
and Protein G
Protein G
Protein G is an immunoglobulin-binding protein expressed in group C and G Streptococcal bacteria much like Protein A but with differing specificities. It is a 65-kDa and a 58 kDa cell surface protein that has found application in purifying antibodies through its binding to the Fc region...
. Thus, it cannot be separated from other components of the assay, for example from other proteins. Additionally, the egg yolk's rich store of lipids
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
and lipoproteins
Lipoprotein
A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...
must be removed. Antibody-containing blood serums, on the other hand, can sometimes be directly used in bioanalysis, i.e., without complicated isolation steps.
Utilization in Foods
Particularly in AsianAsia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
countries, IgY is used as an ingredient in foods. Thus, for example, yoghurt
Yoghurt
Yoghurt, yogurt or yogourt is a dairy product produced by bacterial fermentation of milk. The bacteria used to make yoghurt are known as "yoghurt cultures"...
products are distributed, which contain specific IgY. This hinders the attachment of bacterial
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
Helicobacter pylori
Helicobacter pylori
Helicobacter pylori , previously named Campylobacter pyloridis, is a Gram-negative, microaerophilic bacterium found in the stomach. It was identified in 1982 by Barry Marshall and Robin Warren, who found that it was present in patients with chronic gastritis and gastric ulcers, conditions that were...
in the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. The IgY used for this purpose is extracted from the eggs of immunized hens. Antibodies against Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
and other bacteria, as well as against viruses
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
, are produced in this manner, and employed as a nutritional component for protection against these pathogens
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
.
Literature
- Rüdiger Schade, Irene Behn, Michael Erhard: Chicken Egg Yolk Antibodies, Production and Application. Springer-Verlag, Berlin 2001, ISBN 3-54-066679-6
- G.A. Leslie, L.W. Clem: Phylogeny of immunoglobulin structure and function. 3. Immunoglobulins of the chicken. In: Journal of Experimental Medicine. 130(6)/1969. Rockefeller University Press, S. 1337-1352,
- A. Polson, M.B. von Wechmar, M.H. van Regenmortel: Isolation of viral IgY antibodies from yolks of immunized hens. In: Immunological Communications. 9(5)/1980. Dekker New York, S. 475-493,
- A. Polson, M.B. von Wechmar, G. Fazakerley: Antibodies to proteins from yolk of immunized hens. In: Immunological Communications. 9(5)/1980. Dekker New York, S. 495-514,