Background Autoimmune mechanisms of inflammation in rheumatic diseases are regarded as a certain immune regulation disbalans with high production of autoantibodies. Recently unordinary data are given that antibodies may develop catalytic activity complementary to antigens. The role of catalytic antibodies («abzymes») in rheumatic diseases is the subject of great interest. The aim of the study is to evaluate DNAse activity of polyclonal IgG in patients with different rheumatic diseases as a new marker of autoimmune inflammation.
Objectives The 376 patients with rheumatic diseases (64 with rheumatoid arthritis (RA), 95 with psoriatic arthritis (PsA), 51 with ankylosing spondylitis (AS), 130 with reactive arthritis (ReA) associated with Chlamydia trachomatis urogenital infection), 36 with undifferentiated arthritis (UnA) and 69 healthy persons were examined.
Methods Polyclonal IgGs isolated from sera of patients and healthy persons were investigated. IgG were purified from the sera by combined method of affinity chromatography on protein A column. The experiments, confirming that abzyme activity is the essential quality of polyclonal IgG, were performed. The methods for DNAse activity assessment relied upon rivanol capacity to form a clot with DNA reversely proportional to this acid depolymerisation on the action of DNAse.
Results The levels of DNAse abzyme activity in patients with RA (Me 4.0 units (95%Cl: 3.5-4.0), PsA (Me 3.5 units (95%Cl: 3.2-3.7), AS (Me 1.5 (95%Cl: 1.0-1.5) ReA (Me 2.5 (95%Cl: 2.0-2.5), UnA (Me 3.0 (95%Cl: 2.0-4.0) were higher (p<0.001) than in controls (Me 0.0 units (95%Cl: 0.0-0.5).
We revealed the interconnection (p<0.05) between DNAse IgG activity and morning stiffness (r=0.68), ESR (r=0.52) in RA; disease activity (r=0.53), T-cell count(r=0.40), CRP (r=0,48), ESR (r=0,52) in ReA; physician global assessment of disease activity (r=0.42), CRP (r=0.37), CD4+ cell count (r=-0.49), CD8+ cell count (r=0.50) in UnA; spinal pain (r=0.64), occipital wall distance (r=0.4), BASRI (r=0.47), phagocyte number (r=-0.60; for all p < 0.001) in AS.
We worked out original tests for differentiation of rheumatoid arthritis and reactive arthritis; for differentiation of spondyloarthrites (psoriatic arthritis, reactive arthritis and ankylosing spondylitis) on the basis of DNAse IgG activity assessment, which correspond criteria of «usefull» and «very usefull» for diagnostics in rheumatology .
Conclusions We confirmed the presence of elevated levels of DNAse polyclonal IgG activity in patients with rheumatic diseases in comparison with the health persons and prevalence of these activities in RA and PsA. The multiple interconnections between the DNAse IgG activity, the clinical signs of rheumatic diseases and laboratory findings were detected. We proposed new tests for differentiation of rheumatic diseases on the basis of assessment of DNAse IgG activity.
A.F. Kavanaugh et al. Guidelines for immunologic laboratory testing in the rheumatic diseases: an introduction. American college of rheumatology ad hoc committee on immunologic testing guidelines // Arthritis Rheum. – 2002. – Vol. 47. – P. 429–433.
Disclosure of Interest None Declared