Fc Receptor Proteins

High-quality recombinant Fc receptor proteins for reliable antibody drug research and functional validation.

Fc receptors (FcRs) play a pivotal role in bridging humoral and cellular immunity, influencing immune responses, disease susceptibility, and therapeutic outcomes. Recognizing their importance in antibody function and drug development, KACTUS has developed a comprehensive portfolio of high-quality recombinant Fc receptor proteins—including multiple FcRn and FcγR subtypes and polymorphic variants—using its proprietary SAMS™ Technology platform.

Each protein is rigorously validated for bioactivity through Biolayer Interferometry (BLI) and Surface Plasmon Resonance (SPR), ensuring reliable performance across a wide range of analytical methods. These products empower researchers with robust tools for functional validation of antibody Fc regions, supporting advances in antibody drug discovery and development.

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Background

Role of Fc Receptors in Immunity

FcR is a receptor for immunoglobulin Ig, which can specifically bind to certain regions of Ig's Fc domain to initiate corresponding immune responses, and acts as a bridge between humoral and cellular immunity. The polymorphism of the FcR gene can trigger various biological effects in cells, and is closely related to the development of many immune-related diseases, such as autoimmune diseases Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA). Specific polymorphisms in FcγRIIA (H131R), FcγRIIIA (V158F), and FcγRIIB (T232I) have been associated with altered disease susceptibility and treatment responses in these conditions. The Fc receptor is the most diverse family of proteins in the Fc receptor system, mediating ADCP, ADCC, and CDC effects dependent on antibodies. It plays a key role in activating the immune system and exerting the effects of antibodies.

Classes and Characteristics of Fc Receptors

The most widely used receptors at present are IgG receptors, including FcRn and FcγR. FcγR can be divided into three classes: FcγRI, FcγRII, and FcγRIII. FcγRI has high affinity (10-9M) and is mainly expressed on monocytes, macrophages, and dendritic cells. FcγRII and FcγRIII have low affinity (10-6M) and are widely distributed. FcγRII is further divided into three types based on the structure of the transmembrane domain: FcγRIIa, FcγRIIb, and FcγRIIc, which exist on B cells, macrophages, monocytes, neutrophils, platelets, and other cells. FcγRIIb is the only inhibitory receptor. FcγRIII is mainly present on NK cells, macrophages, and activated monocytes. FcγR can combine with antibody immune complexes to activate immune cells and induce phagocytosis, ADCC, and other effects.

Structure of human Fc Receptor, (Anthony Shock et al. 2020)

FcRn’s Role in Antibody Pharmacokinetics

FcRn can bind to IgG in acidic vesicles (pH 5.0 - 6.5) and protect large antibody molecules from damage. In a blood environment with a pH of 7.4, FcRn releases the large antibody molecules, thus prolonging the half-life of antibodies. This has an important effect on the pharmacokinetics (PK) and effectiveness of antibodies.

Mechanism of FcRn in extending the half-life of IgG, (Derry C. Roopenian, et al. 2007)

Product Validation Data

Our recombinant Fc receptor proteins have been validated for bioactivity using analytical methods including BLI and SPR to ensure functional activity in a range of analytical assays.

Human Fc gamma RIIIA/CD16a (V176) | #FCR-HM13A

Figure 1. Loaded Human Fc gamma RIIIA (V176), His Tag on Anti-His-Biosensor can bind Trastuzumab, hFc Tag with an affinity constant of 96.30nM as determined in BLI assay (Gator® Prime)

Biotinylated Human Fc gamma RI/CD64 | #FRI-HM464B

Figure 2. Biotinylated Human Fc gamma RI, His-Avi Tag captured on CM5 Chip via Anti-His Antibody can bind Trastuzumab with an affinity constant of 0.91 nM as determined in SPR assay (Biacore T200).

Cynomolgus/Rhesus macaque FcRn Protein | #FRN-CM101

Figure 3. Cynomolgus/Rhesus macaque FcRn, His Tag captured on CM5 Chip via Anti-His Antibody can bind Trastuzumab with an affinity constant of 0.18 uM as determined in SPR assay (Biacore T200).

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Available Products

We offer the following off-the-shelf Fc receptor protein catalog products. If you'd like to customize your Fc receptor protein, please submit a custom protein request. To learn more about our products, or for scientific inquiries, contact our team at support@kactusbio.us.