What is IgY?
IgY is an immunoglobulin first described in 1893 when Klemperer1 reported that immunized chickens produce antibodies detectable in their egg yolks as well as their blood. He noted that the concentrations of antibody were similar in both egg yolk and blood, although more recently, it’s been reported that yolk concentrations of IgY are higher2. When Klemperer described chicken immunoglobulins in the late 1800’s, he didn’t name them IgY. For the better part of the 20th century, the predominant immunoglobulin found in chicken blood and egg yolk was known as IgG. It wasn’t until more than 70 years later that the term IgY was coined by Leslie and Clem3, not because the immunoglobulin was found in the yolk, but rather because the avian antibody was sufficiently different and antigenically distinct from the mammalian immunoglobulin counterpart (IgG). It’s now known that IgY is the major immunoglobulin class in birds, reptiles, amphibia and lungfish.