The yolk of eggs laid by immunized chickens has been recognized as an excellent source of antibodies Specific antibodies produced in chickens offer several important advantages over producing antibodies in other mammals. Because a single egg contains as much antibody as an average bleed from a rabbit, this simple, non-invasive approach presents an appealing alternative to conventional antibody production methods. Purification of chicken egg yolk immunoglobulin Y (IgY), the 150 kDa IgG homolog, does not require animal bleeding. In addition, the eggs from immunized chickens provide a continual, daily source of antibody, and this convenient approach offers greater compatibility with animal protection regulations. Due to the phylogenetic distance between birds and mammals, there is greater potential of producing a higher percentage of specific antibody against mammalian antigens when using chickens. Highly conserved mammalian proteins sometimes fail to illicit a humoral response in animals, such as rabbits, that are traditionally used for generating antibodies. Non-specific binding and need for cross-species immunoabsorptions is eliminated since chicken IgY does not cross-react with mammalian IgG and does not bind bacterial or mammalian Fc receptors. There are well defined structural differences of IgY-type immunoglobulins and the IgG of mammals. That includes the molar mass of the heavy chains of the immunoglobulins. The IgY-type immunoglobulins are much less flexible than IgG. Also, the structures of the Fc part of the immunoglobulin isotypes IgY and IgG are different.

The antibody can be used during various purification steps of IgY.