IgY - egg yolk antibody

IgY - main low molecular weight immunoglobulin present in hen's serum and egg yolk in concentration of around 5-20 mg/ml

Molecular mass [kDa] ~ 180 (light chain ~ 25 [kDa] each; heavy chain ~ 65-68 [kDa] each)
Isoelectric point 5.7 - 7.6 (6.6 +/- 0.9 Davalos-Patoja et al. 2000)
Extinction coefficient (i.e. absorbance of a 10 mg/ml solution at 280 nm) are: in 0.3 M KCl=13.18; in 0.1 N NaOH=14.4; in 5M guanidine=12.7
(Leslie and Clem 1969)

Name IgY has been proposed by Leslie and Clem in 1969. The authors showed experimental data proving that IgY molecule is different from IgG ("Phylogeny of immunoglobulin structure and function" G. A. Leslie and L.W. Clem, Journal of Experimental Medicine, Vol. 130, No. 6: 1337-1352, 1969).

Other names for IgY (often misleading) met in literature are: Chicken IgG, Egg Yolk IgG, 7SIgG.

What affinities one can expect from IgY antibodies in comparison with IgG antibodies?
Affinity constant for polyclonal antibodies can not be really measure, since they bind not to one epitope only. Affinity describes a single antibody-antigen interaction, between one antigen binding site and one epitope on the antigen and can be measured for monoclonal antibodies.
Bidning strength of polyclonal antibodies can be described as avidity, which is a combination of the affinities to the individual binding sites and the valency of the antibody. Valency decsribes to how many places the antibody can bind antigen. IgY can perform, as IgG, bi or monovalent, depending upon the size of the antigen. Therefore the binding strength of polyclonal antibody can be high, although the affinity is low.

One can often meet statments, that chicken antibodies have low affinity to the antigens.

However, especially, when antigens are more foreign to the hens than to the rabbits, produced antibodies can have higher multivalency in the chicken, compare to the rabbit, even though the affinity can be lower.
In mammals the Ab diversity is mainly performed by rearranging various gene segments to produce the hypervariable part of the antibody and additionally by somatic mutations. In this way the production of more than a million Ab specificities is possible. In hens the Ab diversity is mainly achieved by gene conversion and in addition by V-J flexible joining and by somatic point mutation as in mammals. In contrast to mammals, in the hens there is only one functional VH- or VL-gene, but in addition there are approximately 25 of the so-called pseudo-V genes (lacking the usual transcription regulatory and signal-recognition sequence).
Therefore hens, can often produce antibodies which will recognize different epitopes than mammalian antibodies would do.

Some interesting features of IgY:

does not bind to rheumatoid factor (an inflammatory response marker) in blood (Larsson et al. 1988)
does not activate mammalian complement factors (Larsson et al. 1992)

This can be of a great advantage in case of assay development for mammalian serum samples
does not bind to cell surface Fc receptor ( Schmidt et al. 1993)
does not bind to protein A (Kronvall et al. 1974) or protein G (Akerström et al. 1985)

latex particles sensitized by IgY molecules do not aggregate by means of the rheumatoid factor (as is the case of IgG antibodies). Moreover IgY-latex complexes have higher colloidal stability than IgG at pH 8 (L.Davalos-Pantoja et al. 2000)

IgY antibodies are selectively, in large amounts passed to egg yolk and therefore NO IgM and IgA impurities can be found in IgY preparations (Schade et al. 2001)
might bind three to five times more secondary antibody ( Horton et al. 1984)

12 eggs contain around 1 gram of total IgY antibodies, what is equivalent to amount of total IgG antibodies present in around 100 ml of serum.

Therefore: A single hen can substitute up to 12 rabbits in antibody production over one year. Around 2,5 g of total IgY antibodies can be produced per hen/month. Amount of antigen-specific antibodies varies from 0,5-10% of total IgY, depending upon the antigen used.

Applications of IgY antibodies.

Chicken antibodies are functionally equivalent to rabbit and other mammalian antibodies and has been successfully used:

to prepare affinity columns for target protein purification (Lee et al. 1997, LiChan et al. 1998)
in Western Blot analysis (Murata et al. 1996, Gutmann et al. 1995)
in ELISA(directly from diluted egg yolk or using purified IgY) (Schwarzkopf et al. 1996, Behn et al. 1996, Lemamy et al. 1999)
biotinylated (Schwarzkopf et al. 1995) or labelled with fluorescein (Lundahl et al. 1996)
in rocket immunoelectrophoresis (Schade et al. 1997)
in immunoprecipitation (Gutmann et al. 1995, Camenisch et al. 1999)
in immunogold labelling (Fortagens et al. 1997)
in immunohistochemistry (Rosol et al. 1993, Schmidt et al. 1993)

IgY purification methods

Different protocols for using IgY

Recommended manual about IgY:
"Chicken Egg Yolk Antibodies, Production and Application" R. Schade et al.2000, Springer-Verlag, Lab Manuals, ISBN 3-540-66679-6.

This book contains description of IgY purification methods, examples of practical experiments using IgY like: Western Blot, ELISA, immunohistochemistry. A basic book for a researcher who wants to use IgY.
Other references about IgY

Secondary antibodies for chicken IgY are available from:

- Abcam
- Jackson
- Pierce
- Promega
- Research Diagnostics
- Sigma
- Zymed

Last changed: 2009-04-02 by WebMaster