ESPE Abstracts

Introduction: Hashimoto's thyroiditis (HT) and Graves' disease (GD) become increasingly common in children's population. Pathogenesis of autoimmune thyroid diseases (AITD) bases on coexistence of genetic predisposition and environmental triggers which finally drive to breakdown of immune tolerance. Many mechanisms in human body moderate process of inflammation. While some of them answer for up-regulation, some agents like B regulatory lymphocytes (Bregs) inhibit spreading of inflammation. Bregs represent 5-10% of whole population of B lymphocytes (CD19⁺) and one of their particular feature is production of interleukin 10 (IL-10) thus they can control inflammation and autoimmunity. The importance of Bregs in the population of children with AITD remain unexplored. The aim of this study was to estimate the expression of Bregs (phenotype CD19⁺CD24^hiCD27⁺ IL-10⁺,CD19⁺IL-10⁺, CD1d⁺CD5⁺CD19⁺IL-10⁺ and CD1d⁺CD5⁺CD19⁺CD24⁺CD27⁺ ) in pediatric cohort with AITD and health controls.

Methods: A total of 100 serum samples were obtained from 53 pediatric patients with GD (N=12 newly diagnosed, mean age 12.5±3.5 and N=17 during methimazole therapy, mean age 12.7±4.4),HT (N=10 newly diagnosed, mean age 13.3±2.9 and N=10 during L-thyroxine therapy, mean age 13.7±3.4) and compared with healthy controls (C) (N=15, mean age 13.1±3.1). The expression of the immune cells populations were analyzed by the four-color flow cytometry using a FASC Canto II cytometer (BD Biosciences). Statistical analysis of the acquired data was performed with the use of GraphPad Prism 5.01 software (GraphPad Software Inc., San Diego, CA).

Results: There is decreasing tendency in number of B10 cells among all B lymphocytes (phenotype CD19⁺) and more widely, also among all lymphocytes, in every studied group, comparing to C. We report notable reduction of IL-10 production in Bregs cells with expression CD19+IL-10⁺, CD19⁺CD24^hiCD27⁺IL-10 and CD1d⁺CD5⁺CD19⁺IL-10⁺ in both untreated and treated AITD. In case of CD1d⁺CD5⁺CD19⁺CD24⁺CD27⁺ impairment in IL-10 production in treated GD and HT groups was noted.

Conclusion: Our data demonstrate that both number and functionality of Bregs in children's AITD are disturbed. The reduction in number of Bregs with CD19⁺CD24^hiCD27⁺ IL-10⁺ and CD19⁺IL-10⁺ expression could be responsible for dysregulation of the immune system and contribute to AITD development.