Fc Fragment Of IgG Receptor Transporter Alpha (FcgRT)

The intestinal epithelium of neonatal mice and rats expresses an Fc receptor (FcRn) that mediates the selective uptake of immunoglobulin G (IgG) in mothers' milk, thereby helping newborn animals to acquire passive immunity. FcRn is structurally similar to the major histocompatibility complex class I molecule, which presents antigenic peptides to T cells. Like the MHC class I molecule, FcRn is made up of a heavy chain (approximately 48 kD) and beta-2-microglobulin. Its heavy chain shows approximately 35% amino acid sequence identity to that of a typical MHC class I molecule. Furthermore, the genomic organizations of the MHC class I and mouse FcRn heavy chain genes are similar in that the signal peptide, the 3 extracellular domains, the transmembrane region, and the cytoplasmic region are all encoded by separate exons.