Marmoset FcRn heterodimer Protein (ICH3034)

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This is a recombinant marmoset (Callithrix jacchus) neonatal Fc receptor (FcRn) presented as a heterodimer, expressed in human embryonic kidney (HEK) 293 cells and validated for surface plasmon resonance (SPR), biolayer interferometry (BLI), and ELISA. The molecule pairs the FcRn alpha chain (encoded by FCGRT) with beta-2-microglobulin (B2M), reconstituting the physiologically relevant, functional receptor complex rather than an isolated subunit. Mammalian HEK293 expression supports native folding and glycosylation, which is important for the pH-dependent IgG- and albumin-binding behaviour that defines FcRn function. Supplied as a research-grade, bulk-capable reagent for research use only (RUO), it is well suited to in-vitro binding, kinetic, and affinity-ranking studies. Marmosets are an increasingly used small non-human primate model in preclinical pharmacology and antibody development, so a species-matched FcRn is valuable for characterising antibody pharmacokinetic properties, engineered Fc variants, and albumin- or Fc-fusion therapeutics across species. The heterodimeric format makes it appropriate for label-free interaction assays that probe Fc-FcRn engagement and cross-species translatability. The neonatal Fc receptor (FcRn) is an MHC class I-like heterodimer comprising an FcRn alpha heavy chain non-covalently associated with beta-2-microglobulin. It binds the Fc region of IgG and, at a distinct site, serum albumin in a strictly pH-dependent manner: engagement is strong at the acidic pH (~6.0) of endosomes and released at near-neutral extracellular pH (~7.4). Through this mechanism FcRn rescues internalised IgG and albumin from lysosomal degradation and recycles them back to the cell surface, extending the serum half-life of both proteins. FcRn also mediates transcytosis across epithelial and endothelial barriers and contributes to maternal-fetal IgG transfer. Because it governs antibody persistence, FcRn is central to the pharmacokinetics of therapeutic monoclonal antibodies and Fc- or albumin-fusion drugs, and is a target for half-life-engineering (Fc mutations that tune FcRn affinity) and for antagonists that lower pathogenic IgG. The marmoset ortholog is relevant for cross-species PK characterisation.