Antibodies play an important role in the innate immune system by circulating in the bloodstream to fight off invading pathogens. IgG is the most prevalent of the five classes of antibodies (IgA, IgD, IgE, IgG, and IgM) and is the only one transmitted from a mother to her offspring. IgG is transported across the epithelium of the placenta by the neonatal Fc receptor (FcRn) (1). FcRn is a 40 kDa protein encoded by the FCGRT gene. FcRn binds to the Fc domain of IgG and transports the antibody in a pH dependent mechanism.
