FCGRT-B2M Heterodimer Protein, Rat (HEK293, His, solution)

The FCGRT-B2M heterodimer protein serves as a crucial cell surface receptor facilitating the transfer of passive humoral immunity from the mother to the newborn. Recognizing the Fc region of monomeric immunoglobulin gamma, it selectively uptakes IgG from milk, particularly at the apical surface of the intestinal epithelium. The formed FcRn-IgG complexes undergo transcytosis across the intestinal epithelium, releasing IgG from FcRn into blood or tissue fluids. This process contributes significantly to effective humoral immunity by recycling IgG and extending its half-life in the circulation. Mechanistically, monomeric IgG binding to FcRn in acidic endosomes of endothelial and hematopoietic cells facilitates the recycling of IgG to the cell surface, releasing it into circulation. Notably, besides its role in IgG homeostasis, the FCGRT-B2M heterodimer also regulates the homeostasis of another abundant circulating protein, albumin/ALB, through interactions with albumin. The FcRn complex, consisting of two subunits, p51, and p14 (equivalent to beta-2-microglobulin), forms an MHC class I-like heterodimer, highlighting its pivotal role in immune and protein homeostasis.