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Calorimetric study of rheumatoid factor binding to human IgG
Molecular Immunology
|October 1, 1984
Summary
Human IgM rheumatoid factor (RF) binds to human IgG with a binding enthalpy of 5.5 X 10(4) J/mole. This interaction involves one RF subunit per IgG heavy chain, regardless of IgG aggregation state.
Area of Science:
- Immunology
- Biophysical Chemistry
Background:
- Rheumatoid factor (RF) is an autoantibody that targets immunoglobulin G (IgG).
- Understanding the binding kinetics and thermodynamics of RF-IgG interactions is crucial for autoimmune disease research.
Purpose of the Study:
- To quantify the enthalpy of binding between human IgM monoclonal rheumatoid factor and native human IgG.
- To investigate if IgG aggregation state influences RF binding thermodynamics.
Main Methods:
- Utilized flow calorimetry for precise measurement of binding thermodynamics.
- Performed thermal titration experiments to determine enthalpy changes.
Main Results:
- The enthalpy of binding was determined to be 5.5 x 10^4 J/mole site.
- A molar ratio of 1 mole of RF to 2.5 moles of IgG was observed, indicating one RF subunit per IgG heavy chain.
- Similar binding enthalpy was found for both native and heat-aggregated IgG.
Conclusions:
- The binding interaction between human IgM RF and IgG is enthalpically driven.
- The binding stoichiometry suggests a specific interaction site on the IgG molecule.
- IgG conformational changes upon heating do not significantly alter the enthalpic contribution to RF binding.