Fcγ Receptor Binding Immunoassay
The expert immunologists at iQ Biosciences perform Fcγ receptor binding immunoassays to assess the interaction between therapeutic antibodies and Fcγ receptors, providing critical insights into antibody function and immune engagement. These assays help evaluate IgG binding to key FcγR variants, including FcγRIIIa (V158/F158) and FcγRIIa (H131/R131), which influence immune effector functions like ADCC and ADCP. Our data support antibody engineering and rapid interrogation of potential Fc activity, enabling clients to refine therapeutic strategies and enhance clinical outcomes.
Our services
- Verify the degree of binding of your therapeutic to the desired human Fcγ.
- Use validated, commercially available immunoassay kits with luminescence measurement by plate reader.
- Perform assays for FcγRI, FcγRIIa (H131), FcγRIIa (R131), FcγRIIIa (V158), and FcγRIIIa (F158) to assess binding against your IgG-containing therapeutic.
- Select appropriate high-binding and low-binding isotype controls with guidance from our immunologists.
- Leverage these highly sensitive biochemical assays to complement and support data from cell-based functional bioassays.
The iQ Experience
Tailored Experiments
Your research is important to us. Our scientists will work through each step of the process with you, including assay design, data analysis, and recommendations for future studies.
Streamlined Process
Simplify your workflow. Bypass the middle-man: at iQ Biosciences, you’ll get immediate access to our biospecimen inventory, saving you both valuable time and money.
Expertise
We’re experts – so you don’t have to be. Augmenting years of experience in immunology and working with immune assays, our scientists stay current with the latest publications and technology.
Exceptional Service
We’re here to help. We know the challenges you’re facing: whether it be through expedited service or our complimentary consulting services, our team is dedicated to helping you reach your goals.
Service overview
How can iQ Biosciences help achieve your goals the smarter way?
Fcγ Receptor Function
Fc gamma receptors (FcγRs) are a group of cell surface receptors that bind to the Fc (fragment crystallizable) region of immunoglobulin G (IgG) antibodies and are expressed on various immune cells. Upon binding to opsonized diseased cells or pathogens, FcγRs mediate effector functions such as antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). While all FcγRs bind IgG and contribute to immune responses, they differ in their IgG-binding affinity, expression across immune cell types, functional roles in immunity (activating vs. inhibitory), and downstream signaling pathways. These differences enable precise regulation of immune processes like phagocytosis, inflammation, and cytotoxicity.
FcγR-family Characteristics
| Feature | FcγRI | FcγRII | FcγRIII |
| Affinity for IgG | High (strong binding) | Moderate (varies by isoform) | Low (requires higher IgG concentration) |
| Cell Types | Macrophages, dendritic cells, neutrophils | B cells, T cells, macrophages, neutrophils | NK cells, macrophages, neutrophils |
| Function | Phagocytosis, cytokine release | Phagocytosis (ADCP), immune modulation, inhibition (FcγRIIb) | ADCC (cytotoxicity) |
| Inhibitory or Activating | Activating | Activating (FcγRIIa), Inhibitory (FcγRIIb) | Activating |
| Structure | Monomeric, single Ig-like domain | Dimeric or tetrameric | Dimeric or monomeric |
| Signal Transduction | Pro-inflammatory, phagocytosis | Pro-inflammatory (FcγRIIa), inhibitory (FcγRIIb) | Pro-inflammatory, cytotoxicity |
A well-characterized polymorphism in FcγRIIIa results in two variants: V158 (high-affinity) and F158 (low-affinity), which significantly influence antibody binding and immune responses.
- V158 Variant: Binds IgG1 and IgG3 with higher affinity, leading to enhanced ADCC and stronger immune responses.
- F158 Variant: Binds IgG with lower affinity, often associated with reduced ADCC and decreased therapeutic antibody efficacy.
This polymorphism is particularly relevant in therapeutic antibody treatments, such as rituximab (anti-CD20), trastuzumab (anti-HER2), and cetuximab (anti-EGFR), where individuals with the V158 genotype often exhibit better clinical responses due to stronger ADCC activity. Understanding a therapeutic antibody’s binding affinity to each FcγRIIIa variant (V158 vs. F158) is critical for predicting clinical efficacy. Antibodies with enhanced binding to the high-affinity V158 variant tend to elicit stronger ADCC responses, while those with weaker binding to F158 may be less effective in promoting immune-mediated tumor or pathogen clearance. This knowledge is essential for antibody engineering, patient stratification, and treatment optimization, ultimately improving therapeutic outcomes.
Additionally, FcγRIIa (CD32a) has two key variants, H131 (high-affinity) and R131 (low-affinity). While both variants exhibit similar binding to IgG1, they differ in their ability to bind IgG2, with the H131 variant demonstrating stronger IgG2 binding.
Check out our C1q binding immunoassay, commonly conducted alongside Fcγ receptor binding assays for a comprehensive assessment of antibody function.
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When no antibody analyte is present, labeled-Tracer binds to the chemi-reactive FcγR target, producing the highest luminescence signal. In the presence of an analyte, non-labeled IgG competes with Trace for binding to the FcγR target, leading to a concentration-dependent reduction in the luminescent signal. (A) These assays include a FcγR Control antibody which is used to generate a standard curve, showing sigmoidal dose-dependent loss of fluorescence signal upon FcγR Control antibody binding. (B) An example of FcγRI binding assay including IgG1 isotype (positive, high binding control) and IgG2 (negative, reduced binding control) controls. (C) An example of FcγRIIa (H131) binding including IgG1 isotype (positive, high binding control) and IgG4 (negative, reduced binding control) controls. (D) An example of FcγRIIa (R131) binding including IgG1 isotype (positive, high binding control) and IgG2 (negative, reduced binding control) controls. (E) An example of FcγRIIIa (F158) binding including IgG1 isotype (positive, high binding control) and IgG2 (negative, reduced binding control) controls. (F) An example of FcγRIIIa (V158) binding including IgG1 isotype (positive, high binding control) and IgG2 (negative, reduced binding control) controls.
Order Information
Pricing
At iQ Biosciences, we understand that each client is unique. Upon quote request, we will provide complimentary consulting services to determine how to tailor our services to best meet your goals. Based on this preliminary assessment, we will be able to provide a price quote.
Expected Timetable
Fit a timetable appropriate to your research goals. We work with you to determine your expected turn-around on a case-by-case basis and ensure that our services fit your needs. Some experiments may require an expedited service – please inquire for more information.
