Antibodies against 4 Atypical Post-Translational Protein Modifications in Patients with Rheumatoid Arthritis.

Area of Science:

• Immunology
• Biochemistry
• Rheumatology

Background:

• Patients with rheumatoid arthritis (RA) exhibit autoantibodies targeting post-translational protein modifications (PTMs).
• The full spectrum of PTMs recognized by RA autoantibodies remains incompletely understood.
• Previous research suggests atypical autoantibodies in RA may target various PTMs.

Purpose of the Study:

• To investigate the presence of autoantibodies against four specific PTMs: chlorination, non-enzymatic glycation, nitration, and homocysteinylation in patients with RA.
• To determine if these PTMs represent significant autoantigens in the context of rheumatoid arthritis.
• To assess the range of PTM autoantigens involved in the autoimmune response in RA.

Main Methods:

• Utilized enzyme-linked immunosorbent assay (ELISA) to detect autoantibodies against modified antigens, including collagen type II, synovial protein extracts, and peptides.
• Assessed reactivity against four PTMs: chlorination, non-enzymatic glycation, nitration, and homocysteinylation.
• Calculated corrected optical density (OD) values by subtracting reactivity against unmodified antigens to identify specific antibody responses.

Main Results:

• Specific antibodies against glycated collagen type II were detected in RA patients compared to healthy controls (p = 0.0003).
• The magnitude of the specific signal for anti-glycated collagen antibodies was small, questioning their clinical relevance.
• No significant autoantibody responses were found against chlorinated, nitrated, or homocysteinylated antigens in RA patients.

Conclusions:

• The four investigated PTMs (chlorination, glycation, nitration, homocysteinylation) do not appear to induce a significant autoantibody response in rheumatoid arthritis.
• The findings suggest that the repertoire of PTM autoantigens in RA is restricted, with limited evidence for antibodies against glycated collagen type II.
• Further research may be needed to fully elucidate the spectrum of PTMs targeted by autoantibodies in RA.