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Avian antibodies in Immunological assays

Avian antibodies, IgY, have many advantages over traditional antibodies from mammalians:


√  Increased Sensitivity

√  Reduced cross-reactivity to IgG

√  Does not bind Rh-factors

√  Does not bind protein A or protein G

√  Does not activate complement factors

√  Does not cause platelet activation


Increased Sensitivity

Since birds are phylogenetically distant from mammals, antibodies with high avidity against conserved mammalian proteins can be raised. Avian antibodies against mammalian antigens are directed against more antigenic epitopes compared with corresponding antibodies produced in mammals. This advantage can be attributed to the fact that that the degree of evolutionary divergence is greater between mammals and birds than between different mammalian species. This difference is particularly pronounced for antibodies against phylogenetically conserved antigens such as peptide hormones.


Reduced cross-reactivity with mammalian IgG antibodies

A mammalian antibody against a mammalian immunoglobulin shows a high degree of cross-reactivity. For example, a rabbit anti-human IgG will cross-react with all other mammalian IgGs except with rabbit IgG. However, it will not cross-react with avian antibodies which are immunologically very different from mammalian IgG. A rabbit anti-chicken IgG will, consequently, not cross-react with other mammalian IgG. As a result the analytical background is reduced by using an avian antibody as the primary antibody and a rabbit anti-IgY as the secondary.


Avian antibodies do not bind to rheumatoid factors

In contrast to mammalian IgG, avian antibodies do not react with rheumatoid factors of mammalian sera. Such reactions often lead to false positive results and are particularly pronounced in cases where mammalian antibodies are used in analyses of serum constituents from patients with autoimmune diseases.


Avian antibodies do not bind to protein A or protein G

Staphylococcal protein A and Streptococcal protein G do not bind to the Fc-part of avian antibodies. Consequently, chicken anti-protein A and chicken anti-protein G react with these proteins in the same way as normal antibodies would. The antibodies will also react with protein A/IgG and protein G/IgG complexes.


Avian antibodies do not activate complement factors

Complement components of a patient's serum are often measured with mammalian antibodies. The product of the reaction is an immune complex that may activate the complement system and bind complement components, leading to erroneous results. The activation of the complement system in these analyses can be avoided by using avian anti-complement components in the assay since the avian antibodies in their reactions with the serum constituents do not activate the mammalian complement system.


Avian antibodies does not cause platelet activation

Immune complexes formed when a mammalian antibody reacts with the antigen may cause complement activation and interactions with Fc-receptors. Both complement activation and Fc-receptor interactions are known to cause platelet activation which is commonly seen when mammalian antibodies are used. This is not the case with avian antibodies, making them suitable for studies of platelet activation by flow cytometry.