SAT0546 IL-17A IS UPREGULATED IN SYSTEMIC SCLEROSIS PATIENTS WITH MIXED ANA IMMUNOFLUORESCENT PATTERN AND MORE THAN ONE POSITIVE ANTINUCLEAR ANTIBODY IN THE SERUM
Authors: Ekaterina Kurteva, Ekaterina Ivanova-Todorova, Kalina Tumangelova-Yuzeir, Georgi Vasilev, Vladimira Boyadzhieva, Nikolay Stoilov, Dobroslav Kyurkchiev
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Systemic sclerosis (SSc, scleroderma) is a rare systemic connective tissue disease characterized by deposition of connective tissue in the skin and internal organs, microvascular impairment and shift in cellular and humoral immune response. More than 95% of the patients produce antinuclear autoantibodies (ANA) years before the first clinical manifestations of SSc. The majority of SSc patients have positive ANA at a high-titre of dilution and nucleolar immunofluorescent staining pattern. The indirect immunofluorescent assay (IFA) on HEp-2 cells is the reference method for ANA screening. According to the International consensus on antinuclear antibody patterns (ICAP) the most relevant and usual patterns ANA patterns have been assigned an alphanumeric code from anti-cell (AC)-1 to AC-28 and are organized into a classification tree. <h3>Objectives:</h3> The aim of the present study is to investigate whether there is a significant correlation between the AC-pattern and the specific autoantibodies in the serum of SSc patients on the one hand, and the percentage of Tregs, Th17 cells and the serum levels of their corresponding cytokines - IL-6, IL-10, TGF-β, IL-17A on the other hand. <h3>Methods:</h3> We enrolled 31 patients who fulfilled the 2013 ACR/EULAR Classification Criteria for SSc at mean age of 47±3 were recruited in the study: 17 with diffuse SSc and 14 patients with localized SSc, respectively. IFA on HEp-2 cells was performed to screen the patients' sera for ANA and to determine the AC staining pattern. Immunoblot method was used to evaluate the specific ANA in patients' sera. We performed flow cytometric analysis of Th17 and Tregs' percentage in the peripheral blood of the patients. The serum levels of IL-6, IL-10, TGF-β and IL-17A were detected by ELISA. <h3>Results:</h3> All patients 'sera were ANA positive at high titer of dilution (above 1:1280). We detected increased IL-17A levels in the serum of patients with AC-3 IFA pattern versus patients positive for AC-29 (18.7 [3.95-99.67] <i>vs</i> 2.5[0.35-8.45], p=0.045). Moreover, IL-17A levels were elevated in the sera with AC-4 IFA pattern when compared to AC-29 (15.6 [4.4-28.9] <i>vs</i> 2.5[0.35-8.45], p=0.033). When opposing patients 'sera, positive for only one ANA, with "simple" AC-IFA pattern, to sera with mixed AC pattern (positive for more than one ANA on immunoblot) we found: increased levels of IL-17A (13.7 [10.2 – 67.2] <i>vs</i> 3.9 [0.4 – 11.6], p = 0.01) and IL-10 (4.4 [2.2 – 5.8] <i>vs</i> 1.5 [0.3 – 3.2], p = 0.043) in the sera with mixed AC pattern. Regarding the Tregs and Th17 cells, we identified a reduced percentage of the CD25negTregs at a marginal trend toward significance in the patients with mixed AC pattern versus the group with simple AC pattern (5.9 [3.2 – 10.6]<i> vs</i> 11.2 [6.1 – 14.3], p = 0.06). <h3>Conclusion:</h3> Although the pathogenetic contribution of ANA in SSc remains unclear, ANA play an important role in the differential diagnosis, risk stratification and assessment of disease activity in SSc. Further research is warranted to clarify the interconnection between the disregulated Th17/Tregs axis and the production of high-high-titer specific ANA in SSc. In the future rheumatologists could benefit from ANA in order to apply the most accurate therapeutic strategy for each patient. <h3>Disclosure of Interests:</h3> None declared