Immunoglobulin Y (IgY)

Immunoglobulin Y (IgY) is the predominant antibody isotype present in birds, reptiles and amphibians, regarded as the evolutionary precursor of mammalian IgG. Produced in avian serum, IgY is transferred and massively accumulated in egg yolks to provide passive maternal immunity for embryos, enabling non-invasive antibody harvesting from eggs of immunized laying hens instead of blood collection from animals. Structurally, IgY weighs approximately 180 kDa with four heavy chain constant domains, distinct from the 150 kDa mammalian IgG which contains three constant domains.

IgY possesses multiple practical merits for research and biotech applications. Due to long phylogenetic distance between birds and mammals, IgY frequently generates strong immune responses against highly conserved mammalian antigens, yielding high specificity polyclonal antibodies. Different from IgG, IgY Fc fragment cannot bind to protein A/G, rheumatoid factors or mammalian Fc receptors, it fails to trigger complement dependent inflammation. Economically, one immunized hen can continuously produce eggs rich in target specific IgY, achieving high antibody yield with relatively low cost and improved animal welfare.

Nowadays, IgY has been widely exploited in multiple fields. It serves as a key research reagent for immunodetection in life science laboratories. In translational scenarios, oral IgY provides passive protection against gastrointestinal pathogens for humans and animals. It also shows promising therapeutic potential for infectious diseases as an alternative strategy to ease antibiotic resistance risks, though further clinical validations are still required for broader clinical adoption.