Heterogeneous IgG interacts with FcRn and its transport across gastrointestinal barrier

The transport of heterogeneous IgG to Fc receptor-expressing leukocytes and serum was investigated by the complement fixation test in mice. The results showed that heterogeneous IgG could be transported into the blood by neonatal Fc receptor (FcRn) on the gut mucosal surface. The interactions between human FcRn and IgG of different animal species were determined. It showed that rabbit IgG had the highest affinity (KD) to human FcRn, and the following species were listed as: human, sheep, horse and cattle. These results indicated the functions of heterogeneous IgG depended on the transport through FcRn, which might protect IgG from being diluted or degraded.