Chicken IgY Antibody Basics

Intro to Chicken Polyconal IgY Antibodies

Antibodies are powerful molecular tools that can be used in a variety of assays where characterization, quantification, localization or identification of a protein (or in some cases, a small molecule) is desired. A key characteristic of antibodies that makes them so useful is their ability to bind tightly and specifically to a desired target molecule. Applications include diagnostic kits (such as pregnancy tests), protein microarrays, immunohistochemistry, immunocytochemistry, western blotting, and ELISA procedures.

The unique properties of chicken IgY antibodies, and the ability to produce them in large quantities in an animal-friendly manner, makes them an attractive option in many antibody-based applications.

Chicken IgY and mammalian IgG antibodies have comparable affinity (the binding strength between a single antibody binding site and a single epitope) and avidity (the overall strength of binding within a multivalent antibody-antigen complex - IgY and IgG are both bivalent). Polyclonal chicken IgY antibodies, just like mammalian polyclonal IgG antibodies, will contain a range of antibodies that potentially recognize multiple epitopes on the immunizing antigen

Although there are some minor physicochemical differences in terms of thermal- and acid-stability when compared with rabbit IgG, chicken IgY antibodies are functionally equivalent to rabbit and other mammalian IgG antibodies in most applications, including Western Blot, immunocytochemistry, immunohistochemistry, ELISA, immunoprecipitation, microarrays, and functional blocking experiments.

For examples of publications using our chicken IgY antibodies, please take a look at our News section and our Customer Success Blog (highlighting custom antibodies).

What is IgY and what is its relationship to IgG?

Chicken immunoglobulin Y (IgY) is the avian counterpart to mammalian IgG, and is the major circulating antibody found in the serum and egg yolk of chickens. In the serum, IgY is found with other antibody isotypes, including IgM and IgA. Egg yolks predominantly contain antibodies of the IgY type; moreover, they contain these antibodies in high concentrations.

IgY is transferred from the blood to the yolk via specific receptors. No significant differences have been observed in terms of structure, capacity to bind antigen, or in avidity between IgY antibodies from serum or egg yolk, (see Pacheco et al (2023) Animals 13, 3130).

There is only one isoform of IgY. This contrasts with IgG, which arises from multiple gamma heavy chain isotypes, and exists in isoforms such as IgG1, IgG2a, and others (the exact range of isotypes varies by mammalian species).

IgY has the same general structure as mammalian IgG, with two heavy chains ("nu" chains at ~67-70 kDa) and two light chains (at 22-30 kDa) (see figure).

The molecular weight of the whole IgY molecule is about 180 kDa, but it often runs as a smear on gels due to the presence of about 3% carbohydrate. Heavy chains of IgY are composed of four constant domains and one variable domain. The light chains contain one variable and one constant domain. IgY lacks the hinge region found in IgG. As in IgG, the antigen binding site is formed from the heavy and light chain variable regions. IgY antibodies contain two identical antigen binding sites and are therefore classed as bivalent antibodies.

For a nice summary of key differences between IgY and IgG, see Pereira et al (2019) International Immunopharmacology 73, 293-303.

Experimental Considerations with IgY

Unlike IgG, the Fc region of IgY does not activate mammalian complement, and does not bind to rheumatoid factor, or mammalian Fc receptors. This can be very advantageous in certain applications (see Why Chicken IgY?).

However, this also means that the IgY Fc region fails to bind to Protein A and Protein G -reagents commonly used for immunoprecipitation experiments using mammalian IgG antibodies. This can be readily overcome by using our PrecipHen® Immunoprecipitation Reagent in place of Protein A/G. This is a Goat Anti-Chicken IgY antibody conjugated to agarose beads. Therefore, chicken IgY antibodies can still be an excellent choice for immunoprecipitation.

Refer to our detailed protocols for further information.