Molecular studies of rheumatoid factor using pseudobioaffinity membrane chromatography

Area of Science:

• Biochemistry
• Immunology
• Materials Science

Background:

• Immunoglobulin G (IgG) and its subclasses play crucial roles in the immune system.
• Rheumatoid factor (RF) is an autoantibody that targets IgG, often forming immune complexes in autoimmune diseases.
• Efficient purification of IgG and autoantibodies is essential for molecular and functional studies.

Purpose of the Study:

• To develop a single-step purification method for total IgG and its subclasses from untreated serum.
• To recover and characterize rheumatoid factor (RF) from patient sera.
• To investigate the catalytic activities of purified IgG, particularly RF, and identify subclass specificity.

Main Methods:

• Utilized L-histidine immobilized on a poly(ethylene vinyl alcohol) hollow fiber membrane for pseudobioaffinity chromatography.
• Employed gentle adsorption and elution conditions for native protein recovery.
• Analyzed purified proteins using SDS-PAGE and assessed catalytic functions using specific substrates (e.g., PFR-MCA).
• Performed rechromatography to determine subclass specificity of catalytic activity.

Main Results:

• Successfully purified total IgG and its subclasses in a single step with efficient recovery.
• Identified a 150-kDa IgG band and a potential 300-kDa RF-bound IgG complex.
• Demonstrated substrate hydrolyzing activity in total IgG from patient sera, exceeding that of healthy controls.
• Indicated IgG2 subclass specificity for the observed catalytic function in rheumatoid arthritis patients.

Conclusions:

• L-histidine immobilized hollow fiber membrane chromatography is an effective method for single-step IgG purification.
• Purified RF exhibits catalytic activities, with a specific association with the IgG2 subclass.
• This purification approach facilitates the study of autoantibodies and their functions in autoimmune diseases.