Fc Receptors
Fc receptors (FcR) are found on the surface of immune cells including macrophages, neutrophils, dendritic cells and natural killer cells. These receptors target the antibody's Fc segment, the permanent part of antibodies.
Fc receptors are type I transmembrane glycoproteins, which are composed of three components: the extracellular, the transmembrane and the intracellular. Extracellular region bound to antibodies; intracellular region signalling. Fc receptors engage antibodies that attach to tainted cells or invaders to trigger a cascade of immune responses that make infected cells recognize and eliminate microbial invaders.
These main types of Fc receptors fall into the following subtypes based on what kind of antibody they are attached to.
| Type | Antibody Type | Major Isoforms | Distribution | Function |
|---|---|---|---|---|
| FcγR | IgG | FcγRI, FcγRII, FcγRIII | Phagocytes, NK cells, dendritic cells, etc. | Mediates ADCC, phagocytosis, and inflammatory responses |
| FcαR | IgA | - | Mucosa-associated immune cells, such as gut phagocytes | Involved in mucosal immunity, pathogen clearance |
| FcεR | IgE | FcεRI, FcεRII | Mast cells, basophils | Involved in allergic reactions, releases histamine and other mediators |
| FcRn | IgG | - | Various tissues, especially placenta | Transports and extends the half-life of IgG |
| FcµR | IgM | - | B cells, other immune cells | Involved in early antibody responses |
| FcδR | IgD | - | B cells | Possibly involved in B cell maturation and activation |
Fcγ Receptors
Fc receptors are the most important of all Fc receptor subtypes, and mediate various immune responses of IgG antibodies, such as cytotoxicity, phagocytosis and inflammation, and play an integral role in the regulation and defence of the immune system.
Depending on the structure, binding affinity to IgG and function as a signalling agent, fc receptors can be subdivided into high-affinity FcRI and low-affinity FcRII, FcRIII, etc. Each subtype plays a different immune regulatory role. Each Fc receptor subtype is listed below with its biological definition in the table below.
| Name | Alternative Name (CD Marker) | Gene | Cellular Avenues | Affinity | Function |
|---|---|---|---|---|---|
| FcγRI/FcγRIA | CD64/CD64a | fcgr1/FCGR1A | Macrophages, Neutrophils, Eosinophils and dendritic cells | High/IgG/mouse and human | Activating |
| FcγRIIa | CD32a | FCGR2A | Monocytes, Neutrophils and NK cells | Low to medium/IgG/human | Activating |
| FcγRIIb | CD32b | fcgr2b/FCGR2B | Macrophages, Neutrophils, basophiles, dendritic cells and B cells | Low to medium/IgG/mouse and human | Inhibitory |
| FcγRIIc | CD32c | FCGR2C | Macrophages, Neutrophils, dendritic cells, mast cells, eosinophils and platelets | Low to medium/IgG/human | Activating |
| FcγRIII | CD16 | fcgr3 | Macrophages, Neutrophils, dendritic cells and NK cells | Low to medium/IgG/mouse | Activating |
| FcγRIIIa | CD16a | FCGR3A | Macrophages and NK cells | Low to medium/IgG/human | Activating |
| FcγRIIIb | CD16b | FCGR3B | Neutrophils and basophils | Low to medium/IgG/human | Activating |
| FcγRIV | ------- | fcgr4 | Macrophages, Neutrophils and dendritic cells | Low to medium/IgG/mouse | Activating |
Biological Functions of Fcγ Receptors
FcγR plays an important role on a variety of immune cells by binding to antibody-antigen complexes. Its specific functions include:
Macrophage activation: When FcR attaches to antibody-antigen complexes, it actually energises macrophages, triggering phagocytosis and antibody-dependent cell-mediated cytotoxicity (ADCC), effectively killing infected cells and tumor cells.
Dendritic cell maturation and antigen presentation: On dendritic cells, FcR binding can facilitate antigen-presenting cell phagocytosis and maturation to elicit T cell responses.
Regulating granulocyte degranulation response: FcR on granulocytes modulates local inflammatory responses and plays a role in the modulation of allergic responses by activating degranulation reactions and secreting vasoactive molecules.
To enhance the ADCC activity of NK cells: NK cell FcR is involved in antibody-dependent cell cytotoxicity that promotes killing via binding to antibodies on target cells.
B cell activation and homeostasis maintenance: B-cells can be activated, proliferated and maintained in an equilibrium by FcR signals that control the activation, proliferation and survival.
Inhibiting T cell overactivation: Through interaction with FcγR, T cells are able to regulate their proliferation and antigen recognition, preventing the risk of autoimmunity caused by overactivation.
Fig.1 The biological functions
of generic Fc gamma
receptor (FcγR).1,3
Fc-Gamma Receptor Binding Assay Services
Creative Biolabs provides FcγR binding assays for researchers to acquire exact kinetic data between antibodies and receptors. This service is a two-way coupled measurement mode, that helps us to select the most suitable measurement protocol to suit your research. We run bioassays for our clients as a stand-alone or integrated development project. Our services include:
- Use appropriate coupling strategies to capture antibodies or Fc receptors
- Qualitative and quantitative kinetic analysis of FcγR/ FcRn interaction, providing rate constants for association and dissociation and affinity (ka, kd, KD)
For customized antibody binding assays, Creative Biolabs offers FcγR binding assays for different IgG antibody subtypes or Fc fusion proteins. This label-free detection system is highly sensitive and run by a trained scientific team to maximize the performance of the assay. Our team is excited to bring this technology to novel antibody therapies and offers multiple assay formats to fit your needs. The detection service covers the following major FcγR subtypes:
- FcγR1/ CD64
- FcγR2a/ CD32a R variant
- FcγR2a/ CD32a H variant
- FcγR2b/ CD32b
- FcγR3a/ CD16a V variant
- FcγR3a/ CD16a F variant
- FcγR3b/ CD16
Fig.2 The family of human FcγRs.2,3
Our Advantages
- High-sensitivity label-free system: The use of advanced label-free detection technology greatly improves the sensitivity of detection and ensures accurate antibody-receptor binding data.
- Bidirectional coupling detection strategy: Through two coupling measurement schemes in different directions, cross-validation of data is achieved, providing optimal detection results and reliable kinetic parameters.
- Professional customized services: Provide personalized experimental scheme design and condition optimization according to customer needs, and equip a professional team to provide full technical support.
- Standardized quality management system: Implement standardized operating procedures and strict quality control to ensure the accuracy and repeatability of experimental data.
FAQs
Q: What is the output format of the test data?
A: We provide detailed kinetic data, including binding affinity, dissociation rate, association rate and other parameters, to provide customers with complete antibody-receptor binding information.
Q: How are samples stored and transported?
A: Short-term storage at 2-8℃, long-term storage at -80℃, use dry ice for transportation, and attach a sample information sheet.
Q: What is the approximate turnaround time for the testing service?
A: The turnaround time will vary depending on the specific testing needs. Generally, the completion time for standard Fcγ receptor binding testing services is 2-4 weeks, and the detailed schedule can be negotiated with the customer based on project requirements.
Q: How to deal with sample test failure?
A: If the test fails due to sample quality issues, we will notify you in a timely manner and discuss solutions.
For more related services and products, please contact us now.
References
- Hamdan, Thamer A et al. "The Diverse Functions of the Ubiquitous Fcγ Receptors and Their Unique Constituent, FcRγ Subunit." Pathogens (Basel, Switzerland) vol. 9,2 140. 20 Feb. 2020, doi:10.3390/pathogens9020140
- Vogelpoel, Lisa TC, et al. "Control of cytokine production by human fc gamma receptors: implications for pathogen defense and autoimmunity." Frontiers in Immunology 6 (2015): 79.
- under Open Access License CC BY 4.0, without modification.
