Background Autoimmune diseases are characterized by tissue damage and loss of function due to an immune response that is directed against specific organs. The role of impaired intestinal barrier function on autoimmune pathogenesis is widely discussed now.
Pancreatic zymogen granule protein 2 Glycoprotein 2 (GP2) has been identified as a major autoantigenic target of the so-called pancreatic antibodies. Recent studies have demonstrated that GP2 is expressed on the apical surface of intestinal membranous cells of the follicle-associated epithelium, and is essential for host-microbial interaction and the initiation of bacteria-specific mucosal immune responses. Antibodies to GP2 have demonstrated diagnostic significance for Crohn's disease. They potentially may be produced in patients with rheumatic disease and be one of missing link between gut inflammation and development the autoimmune process.
Objectives The aim of our study was to investigate the levels of anti-GP2 antibodies classes IgA and IgG in patients with different rhematic diseases and to evaluate their pathogenic and diagnostic significance.
Methods We studied 90 persons: 52 patients with spondyloarthropathies (SpA) (38 patients with axial SpA, 14 – with peripheral SpA), 21 patients with rheumatoid arthritis (RA), 16 other patients (4 - with systemic lupus erythematous, 1-with systemic sclerosis, 3 – with gout, 8 – with inflammatory back pain (IBP). All patients are fulfilled respective latest classification criteria. Nobody from the patient has intestinal discomfort, obstipation, diarrhea, history or presence inflammatory bowel disease.
Levels of anti-GP2 antibodies (IgA and IgG classes) have been detected by ELISA (Medipan GmbH, Germany). Cut-off levels, determined by manufactures, are ≥20 U/ml.
Results The levels of anti-GP2 IgA in patients with axial SpA (Me 5.63; 95%CI 3.26-15.37), peripheral SpA (Me 2.41; 95%CI 0.59-12.65), RA (Me 6.78, 95%CI 2.25-14.73), IBP (Me 3.43 (95%CI 1.38 -6.37), not differed (p>0.05) between each other.
The levels of anti-GP2 IgG in patients with axial SpA (Me 3.39; 95%CI 2.14-4.23) not differed (p>0.05) from patients with peripheral SpA (Me 1.48, 95%CI 0.85-5.34), RA (Me 3.97; 95%CI 2.23-10.00), IBP (Me 1.39 (95%CI 0.63–4.92). The levels of anti-GP2 IgG in patients with RA were higher than in patients with peripheral SpA (p=0.0082) and IBP (p=0.0148).
We revealed that determination anti-GP2 IgA levels (2.44 and more units) might be applied for discrimination of axial SpA from peripheral SpA (sensitivity 76.32% (95%CI: 59.80-85.50), specificity 51.14% (95%Cl: 28.90-82.20), PLR 1.78, NLR 0.41 p=0.0268). The detection of anti-GP2 IgG levels (2.05 and more units) might be implicated for discrimination of axial SpA from peripheral SpA (sensitivity 71.05% (95%CI: 54.10-84.60), specificity 71.43% (95%CI: 41.90-91.40), PLR 2.49, NLR 0.41, p=0.0385).
Conclusions First obtaining data may be initial steps in understanding several interrelationships between gut inflammation and the development of autoimmune diseases, which can have the implementation in clinical practice. It is necessary to continue study in this direction for finding new data.
Disclosure of Interest M. Volkava: None declared, A. Kundzer: None declared, I. Generalov: None declared, J. Kobec: None declared, D. Roggenbuck Shareholder of: Medipan GmbH