Related Experiment Videos
Binding characteristics of dimeric IgG subclass complexes to human neutrophils
T W Huizinga1, M Kerst, J H Nuyens
1Central Laboratory, Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Journal of Immunology (Baltimore, Md. : 1950)
|April 1, 1989
Summary
Human neutrophils bind IgG3 immune complexes faster than IgG1 complexes, with both interacting via Fc gamma receptors (FcγR). Neutrophil FcγRIII and FcγRII mediate this binding, influencing affinity and capacity.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Immune complexes play a crucial role in immune responses.
- Understanding the interaction between immune complexes and immune cells is vital for deciphering immune regulation and pathology.
- Human immunoglobulin G (IgG) subclasses exhibit distinct effector functions mediated by Fc gamma receptors (FcγR).
Purpose of the Study:
- To characterize the structure of immune complexes formed with human IgG paraproteins and a specific anti-kappa light chain monoclonal antibody (mAb).
- To investigate the binding kinetics and affinity of different human IgG subclass complexes to human neutrophils.
- To elucidate the role of Fc gamma receptors (FcγR) on neutrophils in mediating the binding of these immune complexes.
Main Methods:
- Preparation and characterization of IgG-mAb immune complexes using ultracentrifugation, gel filtration, and radioimmunoassay (RIA).
- Quantitative analysis of immune complex binding to human neutrophils at 4°C via RIA.
- Competition assays using labeled and unlabeled immune complexes and blocking studies with monoclonal antibodies against FcγRII and FcγRIII.
Main Results:
- Characterized immune complexes as saturated tetramers of two IgG molecules cross-linked by two F(ab')2 fragments of the mAb.
- Human neutrophils exhibited significantly faster binding of IgG3 complexes compared to IgG1 complexes; IgG2 and IgG4 binding was undetectable.
- Neutrophils bound similar quantities of IgG1 and IgG3 complexes, with FcγRIII being essential for binding and FcγRII modulating affinity, suggesting simultaneous binding to both receptors.
Conclusions:
- Human neutrophils bind IgG3 immune complexes more rapidly than IgG1 complexes, with FcγRIII playing a primary role and FcγRII a secondary role in binding.
- Neutrophil Fc gamma receptors (FcγR) do not exhibit IgG subclass specificity in binding these complexes.
- Immune complexes can simultaneously engage FcγRIII and FcγRII on neutrophils, highlighting a complex mechanism of immune cell activation.