[IgA rheumatoid factor formation in connection with complement activation and circulating immune complexes in chronic...

Area of Science:

• Rheumatology
• Immunology
• Biochemistry

Background:

• Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint inflammation.
• Immunological markers like IgA-rheumatoid factor (IgA-RF) and complement components are implicated in RA pathogenesis.
• Circulating immune complexes (CIC) are also studied in relation to disease activity.

Purpose of the Study:

• To investigate the relationship between IgA-rheumatoid factor (IgA-RF) levels and complement component C3a in patients with established rheumatoid arthritis.
• To explore the correlation between IgA-RF and circulating immune complexes (CIC).

Main Methods:

• Enzyme immunoassays were used to measure IgA-RF, complement component C3a, and CIC in plasma and serum samples.
• 81 patients with established rheumatoid arthritis were included in the study.
• Specific assays included C1q binding and Raji Cell Replacement assays for CIC.

Main Results:

• Serum levels of complement component C3a were significantly higher in patients with high IgA-RF compared to those with low IgA-RF (p < 0.02).
• A significant positive correlation (r = 0.38; p < 0.001) was found between IgA-RF production and C3a activation.
• A weaker correlation was observed between CIC and IgA-RF levels, suggesting CIC are not closely related to IgA-RF production in RA.

Conclusions:

• The findings suggest a significant association between IgA-RF production and complement activation (C3a) in rheumatoid arthritis patients.
• This association may be linked to antibody production and complement activation during inflammatory processes in RA.
• While CIC levels showed a weaker correlation, an indirect connection via inflammation and T-cell activation is possible.