Fc (IgG1): FcRn Inhibitor Screening Colorimetric Assay Kit
The Fc (IgG1): FcRn Inhibitor Screening Colorimetric Assay Kit is designed for screening and profiling neutralizing antibodies or inhibitors of the interaction between Fc (IgG1) and human FcRn. This kit comes in a convenient 96-well format, with purified Biotinylated-FcRn complex (Fc receptor amino acids 24-297 and B2M amino acids 21-119) and Fc (IgG1) (amino acids 100-330) proteins, Streptavidin-HRP, and assay buffers for 100 reactions.
The assay mechanism is described next. Fc (IgG1) is coated on a 96-well plate overnight. After blocking, the protein is pre-incubated with the inhibitor or neutralizing antibody. Upon subsequent incubation with Biotin-FcRn, the plate is treated with Streptavidin-HRP followed by addition of a colorimetric HRP substrate to produce color, which can be quenched and measured using a UV/Vis microplate reader.
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- PBS (Phosphate Buffered Saline)
- 1N HCl (aqueous)
- Rotating or rocker platform
- UV/Vis spectrophotometer microplate reader capable of reading absorbance at λ=450 nm
| Catalog # | Name | Amount | Storage |
| 71456 | IgG1, Fc (Human)* | 2 x 5 µg | -80°C |
| 71283 | FcRn (FCGRT/B2M), His-Avi-Tag, Biotin-Labeled* | 2 x 5 µg | -80°C |
| 79311 | 3X Immuno Buffer 1 | 50 ml | -20°C |
| 78502 | Blocking Buffer 6 (pH 5.5) | 50 ml | +4°C |
| 79742 | Streptavidin-HRP | 10 µl | +4°C |
| 79651 | HRP Colorimetric Substrate | 10 ml | +4°C |
| 79964 | Clear 96-well microplate | 1 | Room Temp |
*The initial concentration of both FcRn and Fc (IgG1) is lot-specific and will be indicated on the tube containing the protein.
Neonatal Fc receptor for IgG (FcRn) is a heterodimeric protein. FcRn consists of the Fc Gamma Receptor and Transporter encoded by the FCGRT gene, associated with beta-2-Microglobulin (B2M). FcRn binds to the Fc region of monomeric immunoglobulin G (IgG). It is expressed in over 25 tissue types, with high expression levels observed in the spleen and intestine. In the placenta, it transports IgGs from mother to fetus. FcRn contributes to an effective humoral immunity by protecting IgGs from degradation, recycling them and extending their half-life in circulation. In addition to IgGs, it regulates the homeostasis of serum albumin.
The function of FcRn can be exploited by engineering therapeutic antibodies to increase their binding to FcRn, thereby improving their half-life and therapeutic efficacy. For example, an antibody cocktail that contains Fc mutations and an extended half-life (Evusheld) is used to treat COVID-19. The first-in-class drug, Enbrel, a TNF-alpha/Fc fuses Fc portions to a therapeutic protein to increase their half-life. There are now several other drugs in clinical using similar strategies.
Conversely, FcRn is a potential therapeutic target for autoimmune diseases. Disrupting the FcRn/IgG interaction is expected to increase the overall clearance of IgGs, including disease-causing autoantibodies. Engineered Fc fragments or neutralizing IgGs that bind to FcRn with high affinity through their Fc region are currently undergoing clinical trial. The first FDA-approved drug targeting FcRn (efgartigimod) is now used to treat myasthenia gravis, an autoimmune neuromuscular disease caused by the presence of autoantibodies against acetylcholine receptor, providing proof-of-concept in favor of this strategy.
Dall'Acqua W.F., et al. 2002 J Immunol. 169(9): 5171-80
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