Maternal Transfer of Immunoglobulins into Egg Yolks of Birds

Abstract

In avian species, maternal IgY transferred across egg yolks from mother to offspring plays a key role to protect the hatching chicks against pathogenic attacks. The process of avian maternal IgY transfer is divided into two steps: the first step is the transfer from the maternal circulation to the egg yolks of developing oocytes in the maternal body, and the second step is the transfer from the egg yolks to the embryonic circulation in the developing eggs. The second step relies on IgY-Fc receptor, FcRY, expressing on the yolk sac membrane. However, in the first step, the molecular basis of IgY transfer is still unknown. This review focused on the structural requirements of IgY and heterologous immunoglobulin such as human IgG for transferring into egg yolks of birds, and a plausible molecular mechanism for immunoglobulin uptake in ovarian follicles were discussed. Recent research revealed existence of a selective IgY transfer system that recognizes Cυ3/Cυ4 interface of IgY in ovarian follicles of birds.