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Neonatal Fc Receptor Binding Studies with Lumit™ Immunoassays

The Lumit™ FcRn Binding Immunoassay is a homogeneous, add-mix-read immunoassay used to measure antibody binding to the human neonatal Fc receptor (FcRn). Employing NanoBiT® enzyme complementation technology, this novel luminescent assay is fast, sensitive and easy to perform. Unlike other technologies that involve immobilization of FcRn or antibodies, the Lumit™ FcRn Binding Immunoassay is entirely solution-based, eliminating the possibility of surface artifacts.

Lumit™ FcRn Binding Immunoassay Overview

FcRn Function

The neonatal Fc receptor (FcRn) is expressed in the endosomal compartments of a variety of cell types, including vascular endothelium and antigen-presenting cells (APCs). FcRn binds to the Fc region of immunoglobulin G (IgG) antibodies at acidic pH within endosomes. In utero, FcRn acts to transfer maternal IgG to the developing fetus. In adults, it is involved in recycling of IgG and albumin. Recycling by FcRn is the primary reason for the long half-life (several weeks) of IgG and albumin in serum. Furthermore, a critical factor for the success of therapeutic antibodies is their extended half-life, which contributes to better efficacy and long dosing schedule. Therefore, the FcRn-IgG interaction is a key parameter to optimize and track throughout the antibody drug development process.

Assay Principle

The Lumit™ FcRn Binding Immunoassay is a novel homogeneous (no-wash) competition assay to measure the interaction between human FcRn and Fc proteins, including antibodies. NanoLuc® Binary Technology (NanoBiT®) is a structural complementation reporter designed for biomolecular interaction studies. The NanoBiT® system is composed of two subunits, Large BiT (LgBiT; 18kDa) and Small BiT (SmBiT; 11 amino acid peptide), that have been optimized for stability and minimal self-association. In the Lumit™ FcRn Binding Immunoassay, a Human IgG1 labeled with LgBiT (Tracer-LgBiT) is used as the tracer. A C-terminal biotinylated human FcRn bound to Streptavidin-SmBiT (hFcRn-Biotin-SA-SmBiT) is used as the target. In the absence of an antibody analyte sample, Tracer-LgBiT binds to the hFcRn-SmBiT target resulting in maximum luminescence signal. In analyte samples, unlabeled IgG will compete with Tracer-LgBiT for binding to the FcRn target, resulting in a concentration-dependent decrease in luminescent signal.



  • No wash, no transfer: The simple add-mix-read protocol can be performed directly on cell cultures.
  • Rapid time to results: Get results in under an hour.
  • Scalable and high throughput: Perform the assays in low volumes in 96-well or 384-well plates; precoated plates not required.
  • Luminescence detection: Use a standard plate-reading luminometer; no specialized instruments or modules required.

The Lumit™ FcRn Binding Immunoassay is available as early access material. Contact us for a current list of available kits and ordering information.

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