Creative Biolabs is a leading service provider that focuses on antibody development, engineering, characterization, analysis, and application. With extensive experience in antibody functional analysis, our scientists are able to provide superior FcγRIIIb binding assay services for global clients. Especially, we can deal with not only antibodies but also Fc-fusion proteins.
FcγRIIIb, also known as CD16b, is an isoform of the human IgG Fc receptor CD16 (FcγRIII, another isoform is FcγRIIIa) that provides an important link between innate and adaptive immunity. Unlike FcγRIIIa that is expressed on mast cells, macrophages, and natural killer cells as a transmembrane receptor, FcγRIIIb is only expressed on human polymorphonuclear leukocytes (neutrophils) and eosinophils. Actually, FcγRIIIb is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein with low affinity and no transmembrane domain. It is the only Fc receptor anchored to the plasma membrane and plays a critical role in triggering calcium mobilization and neutrophil degranulation. As a result, FcγRIIIb is unable to associate with FcRγ or the ζ-chain due to the absence of the cytoplasmic domain. Instead, FcγRIIIb together with FcγRIIIa bind to the Fc portion of IgG antibodies in the immune-complexed form rather than the soluble form and functionally activate phagocytosis and degranulation, thus enabling the clearance of pathogens by neutrophils.
Investigations have indicated that increased expression of FcγRIIIb results in higher binding and uptake of immune complexes, subsequently causing illness and disorders. Moreover, mutations and copy-number variations of FcγRIIIb-encoding FCGR3B gene or FcγRIIIb polymorphisms have been reported to be associated with disorders such as glomerulonephritis, autoimmune diseases, and even clinical malaria.
Fig.1 Structure, cellular distribution and IgG isotype-binding affinity of human FcγRs. (Smith, 2010)
Concerning the critical features and functions of FcγRIIIb, it is very necessary to characterize the binding affinity of antibody Fc fragment to FcγRIIIb receptor. This has drawn much attention and shown great importance in therapeutic antibody development, primarily due to the association with the transportation, catabolism, and toxicities of antibodies.
Creative Biolabs has developed a full range of testing platforms for FcγRIIIb binding assays by modern biological approaches, including ELISA, flow cytometry, biacore surface plasmon resonance (SPR), and octet bio-layer interferometry (BLI).
Case Study
Fig.2 Binding and fitting curves between sample-1 with FcγRIIIb/CD16b (NA1) at different concentrations. (Creative Biolabs)
Fig.3 Binding and fitting curves between sample-1 with FcγRIIIb/CD16b (NA2) at different concentrations. (Creative Biolabs)
Table.1 SPR result summary between sample-1 with FcγRIIIb/CD16b subtypes. (Creative Biolabs)
| Method | Ligand | Capture Level (RU) | Analyte | Analyte Conc. | ka (1/Ms) | kd (1/s) | KD (M) | Rmax (RU) | Chi² (RU²) | Fit method |
| His Capture | Human FcγRIIIb/CD16b (NA1) | 45.4 | Sample-1 | 39.063-10000 nM | NA | NA | 3.14E-06 | 145.6 | 2.78 | Steady-state affinity |
| His Capture | Human FcγRIIIb/CD16b (NA2) | 43.2 | Sample-1 | 39.063-10000 nM | NA | NA | 1.99E-06 | 130.5 | 2.99 | Steady-state affinity |
Creative Biolabs is a well-recognized expert who has been devoted to the field of antibody development for over a decade. Besides FcγRIIIb binding assays, we can also offer antibody binding assays targeting other Fcγ receptors (FcγRIIIa, FcγRIIb, FcγRIIa, and FcγRI), FcRn, and complement protein C1q. Moreover, we offer cell-based assays, including antibody-dependent cytotoxicity (ADCC), antibody dependent cellular phagocytosis (ADCP), and complement dependent cytotoxicity (CDC), to not only characterize your product with respect to receptor/complement binding but also investigate the mechanism of action.
Our scientists are confident in offering satisfying results and services to promote your research or projects. For more information, please contact us or send us an inquiry.
Reference
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