Transfer of Chicken Immunoglobulin Y (IgY) from the Hen to the Chick

Abstract

Chicks depend on maternal antibodies as the main source of passive natural humoral protection until they become immunocompetent. Immunoglobulin Y (IgY), the avian homologue of mammalian IgG is transferred from the circulation of the hen into the egg yolk and then absorbed by the embryo. In the post-hatching period, protein integrity within the yolk sac is critical for normal absorption of the yolk sac content and for IgY transfer to the circulation of the chick. Factors affecting transfer of IgY to the chick may threaten the chick's immune status and increase disease susceptibility during the early post-hatching period. Here we review basic concepts of IgY with special emphasis on the mechanisms of IgY transfer to egg yolk and yolk sac during embryonic development and first days post-hatching.