Aves Labs, Inc.

Chicken IgY is the major circulating antibody found in chickens and is the avian counterpart to mammalian IgG’s. IgY’s are equivalent to IgG’s in most experimental applications, including Western Blotting, ELISAs, immunohistochemistry, immunocytochemistry, and function blocking experiments.

IgY’s have the same general structure as a mammalian IgG, with 2 heavy (“nu” chains, ~67-70 kDa) and 2 light chains (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’s are composed of 4 constant domains and one variable domain, which contains the antigen-binding site. Unlike the gamma-chains of IgG, however, the heavy chains of IgY’s lack Fc domains, which means that IgY’s don’t fix complement nor bind protein A or protein G. Chickens also produce an alternatively-spliced form of the heavy chain in which the Cnu3 and Cnu4 domains are deleted. In some individual hens, this F(ab)2-like heavy chain can be seen running at 40 kDa in SDS-(10%) polyacrylamide gels.