Background Primary Sjögren syndrome (PSS) is one of the most common auto-immune systemic rheumatic diseases although its prevalence anging between 0.6 and 1.7%. PSS affects exocrine glands and lead to sicca syndrome. Interleukin-10 (IL-10) is a pleiotropic cytokine that is involved in the inflammation process of PSS.
Objectives The aim of our study was to determine in a Tunisian population, clinical and biological characteristics of patients with primary PSS, allelic and genotypic frequencies of (-1082G/A, -819 C/T and -592 C/A) polymorphisms in IL-10 gene and to evaluate the association of these polymorphism with PSS.
Methods The population we studied consisted of 242 subjects with female predominance (average age at diagnosis =49 years), divided into 84 PSS patients (fulfilling the revised AECG criteria 2002 and/or ACR proposed criteria 2012),recruited in the internal medicine department of the Rabta hospital and 158 controls recruited in the Greater Tunis. Il 10 level was assessed by ELISA. Polymorphisms genotyping of the IL-10 gene was done using PCR-RFLP technique.
Results Il10 plasma level was lower in PSS patients (23.71pg/ml, n=73) compared to healthy volunteers (42.27pg/ml, n=60) and the difference was statistically significant (p=0.01).
The genotype frequencies of our population respected Hardy-Weinberg equilibrium distribution both in patients by primary SS than in controls. In PSS patients, the genotype frequencies of -592C/A are 53% for the CC genotype, 41% for the CA and 6% for the AA genotype. In controls these frequencies are respectively 60.3%, 32.9% and 6.8%. The genotype frequencies of -1082 G/A are 29.6% for the AA genotype, 63% for the AG and 7.4% for the GG genotype. In controls these frequencies are respectively 41.5%, 52.1% and 6.3%.
The genotype frequencies of -819 C/T are 47.6% for the CC genotype, 43.9% for the CT and 8.5% for the TT genotype. In controls these frequencies are respectively 41.5%, 52.1% and 6.3%.
No significant differences in genotypic frequencies were observed between cases and controls in the three polymorphisms.
Statistical analysis preformed revealed that there was neither protective nor aggravating hapoltype. However ATC haplotype seems to have a protective impact in controls (p=0.06 and OR=0.20)
Conclusions IL10 level was significantly higher in PSS patients in precedent studies (1) (2). In our case Il10 level was associated with PSS in Tunisian patients but it was statistically lower than controls. Our results show that the three polymorphisms of gene of IL-10 are not a marker of SGS in the Tunisian population. This result might be explained by allelic variation or ethnic group.
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Vazquez-Villamar M, Palafox-Sanchez CA, Munoz-Valle JF, Valle Y, Orozco-Barocio G, Hernandez-Bello J, et al. Analysis of IL10 haplotypes in primary Sjogren's syndrome patients from Western Mexico: Relationship with mRNA expression, IL-10 soluble levels, and autoantibodies. Human immunology. 2015;76(7):473–9.
Disclosure of Interest None declared