Mouse FcRn heterodimer Protein (In Vivo Grade, Ultra-Low Endotoxin) (ICH3029)

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This is a recombinant mouse FcRn (neonatal Fc receptor) heterodimer, comprising the FcRn alpha chain (encoded by Fcgrt, UniProt Q61559) non-covalently paired with beta-2-microglobulin (B2m, UniProt P01887). It is expressed in human embryonic kidney (HEK) 293 cells, which support proper folding, disulfide bonding and glycosylation of this mammalian complex. The protein is validated for surface plasmon resonance (SPR), biolayer interferometry (BLI) and ELISA, making it well suited to characterising pH-dependent IgG and albumin binding, ranking Fc-engineering variants, and measuring antibody or Fc-fusion recycling potential. Supplied at ultra-low endotoxin (<0.5 EU/mg), it is appropriate for sensitive cell-based and binding studies where endotoxin can confound results. This is a bulk, research-use-only (RUO) reagent for functional and biochemical research rather than a therapeutic or diagnostic product. As a soluble ectodomain heterodimer, it is intended for in-vitro and cell-based work; it is not an antibody and is not administered to animals. FcRn, the neonatal Fc receptor, is an MHC class I-like molecule formed by an FcRn alpha heavy chain paired with beta-2-microglobulin. It is the central regulator of IgG and serum albumin homeostasis. FcRn binds the Fc region of IgG (and, at a distinct site, albumin) in a strictly pH-dependent manner: binding is strong in the acidified early endosome (pH ~6.0) and negligible at physiological pH ~7.4. After pinocytosis, bound IgG and albumin are diverted from lysosomal degradation and recycled back to the cell surface, where near-neutral extracellular pH triggers release. This salvage pathway gives IgG and albumin their long serum half-lives and mediates materno-fetal and neonatal IgG transfer across epithelia. FcRn is therefore a key determinant of antibody pharmacokinetics and the target of half-life-extension Fc engineering and FcRn-blocking therapeutics.