IgY versus IgG

what are the differences?

Avian IgY is genetically and structurally different from its mammalian counterpart IgG. 
As igG, IgY has 2 heavy chains and 2 light chains shaped in the characteristic Y-shape with an antigen valency of 2. Functionally, they play similar biological roles. IgG and IgY are both major immunoglobulins providing defense against infectious agents and appearing in the bloodstream at high concentrations following exposure to an antigen. 

IgY has a higher molecular weight due to an extra heavy chain constant domain. IgY also has a unique glycosylation pattern. However, there is little or no immunological cross-reactivity between IgY and mammalian IgG. In chickens IgY is actively transported to the egg yolk where the IgY concentration is ultimately higher than in blood. 

Why use IgY in immunological assays?

• IgY is a highly specific polyclonal antibody suitable for a range of immunoassays and applications. Using chicken antibodies in immunological assays may improve selectivity, sensitivity and reliability of your diagnostic product. This is largely attributed to the inherent low degree of interferences and good stability of IgY.

• Chickens are domesticated birds that genetically differ significantly from humans and other mammals. Hence, chickens may raise a stronger immune response against human antigens than for instance rabbits, mice or goats. Chickens often recognize a larger part of the antigen as foreign and may be used to obtain antibodies against human antigens in cases where antibody production in mammals has failed

• There is no need to bleed or sacrifice animals

• NABAS production procedures are far more effective than existing procedures in mammals. The consequence is significantly lower cost for high volume output.

• Reduced cross-reactivity compared with IgG antibodies (against mammalian biomarkers).

• IgY reduces background by not binding to rheumatoid factors. Rheumatoid factors of mammalian sera may react with the Fc domain of IgG, causing false positive results. In contrast to IgG, IgY does not bind to rheumatoid factor.

• IgY does not activate the mammalian complement system. Complement components in a patient's serum are often measured using mammalian antibodies (IgG). The immune complex formed may in turn activate the complement system and bind to complement components, leading to false results. This can be avoided by using chicken antibodies against the anti-complement components.

• IgY does not bind to mammalian Fc receptors. Both complement activation and Fc-receptor interactions are known to cause platelet activation, which is commonly seen in assays using mammalian IgG antibodies. This is not the case with chicken antibodies, making IgY suitable for studies of platelet activation by flow cytometry.

• In contrast to IgG, Staphylococcal protein A and Streptococcal protein G do not bind to the Fc domain of IgY. Consequently, chicken antibodies against protein A or protein G will not have unspecific binding to these proteins.

Scientific references IgY

For more information about chicken antibody production and use, we have listed some relevant scientific references on the topic below.

• IgY: clues to the origins of modern antibodies. Warr GW, Magor KE, Higgins DA. Immunol Today. 1995 Aug;16(8):392-8.

• Generation and application of chicken egg-yolk antibodies, M. Tini, U.R. Jewell, G. Camenisch, D. Chilov, M. Gassmann. Comparative Biochemistry and Physiology Part A 131 (2002) 569–574.

• IgY: a promising antibody for use in immunodiagnostic and in immunotherapy. Dias da Silva W, Tambourgi DV. Vet Immunol Immunopathol. 2010 Jun 15;135(3-4):173-80.

• Chicken egg yolk antibodies (IgY-technology): a review of progress in production and use in research and human and veterinary medicine. Schade R, Calzado EG, Sarmiento R, Chacana PA, Porankiewicz-Asplund J, Terzolo HR. Altern Lab Anim. 2005 Apr;33(2):129-54.

• Comparison between chicken and rabbit antibody based particle enhanced cystatin C reagents for immunoturbidimetry. Hansson LO, Flodin M, Nilsen T, Caldwell K, Fromell K, Sunde K, Larsson A. J Immunoassay Immunochem. 2008;29(1):1-9.

• Performance Characteristics of a Cystatin C Immunoassay with Avian Antibodies. Kathrin Sunde, Tom Nilsen and Mats Flodin. Upsala J Med Sci 112 (1): 21–37, 2007

• Molecular stability of chicken and rabbit immunoglobulin G. Shimizu M, Nagashima H, Sano K, Hashimoto K, Ozeki M, Tsuda K, Hatta H. Biosci Biotechnol Biochem. 1992 Feb;56(2):270-4.

• Reconciling the structural attributes of Avian Antibodies. Paul J Conroy et al. J Biol Chem. 2014 May 30;289(22):15384-92.

• Chicken Antibodies: Taking advantage of Evolution – A review. Larson A, Bålow R-M, Lindahl T.L, Forsberg P-O. (1993) Poultry Science, 72:1807-1812.

• Chicken anti-protein G for the detection of small amounts of protein G. Larsson A. and Lindahl T.L. (1993) Hybridoma, 12, 143-147.

• Chicken antibodies: A tool to avoid interference in immunological assays. Larsson A. and Lindahl T.L. (1993). Avian immunology in progress, 62, 97-102.

• Chicken IgY: Utilizing the evolutionary difference. Larsson A.and Sjöquist J.(1990) Comperative Immunology, Microbiology and Infectious Diseases 13, 199-201.

• The chicken egg, an antibody source. Lösch U.,Schranner I., Wanke R.and Jurgens L.(1986). J.Vet.Med.33, 609-619.