Μελέτη των Τ ρυθμιστικών κυττάρων σε συγγενείς ατόμων με σακχαρώδη διαβήτη τύπου 1

Abstract

Introduction: Regulatory T cells are considered to have a primary role in maintaining theimmune homeostasis. A hallmark in Tregs is the high expression of the transcription factor,FoxP3 and its negative correlation with the expression of CD127.A new approach to humanTregs was presented by Shimon Sakaguchi and his team in 2009. According to the authors, theFoxP3+ Τ cells are not a homogenous population and they can be separated in three distinctsubpopulations. Studies on the percentage and phenotypic changes of Tregs in T1D, reported a a lack in the suppressive ability of Tregs from T1D patients compared to controls. First degree relatives (FDR) of T1D patients are considered a high risk group for the disease and many studies were conducted on FDR.Objective: The aim of our study was to investigate the frequency and the phenotype of Tregs in FDR compared to healthy control, in order to investigate any possible correlation to the disease appearance.Materials and methods: 38 FDR (17 siblings, 5 children, 9 mothers and 7 fathers) and 45 healthy controls were recruited. Four colour flow cytometry was performed in whole fresh blood samples and HLA class II typing was tailored.Results: First, we tried to verify by independent means the estimated percentage of Tregs based on the phenotype CD4intCD25highCD127-/low. The percentage of Tregs was not significantly different between FDRs and controls. This was also the case, when we compared the percentages of the different subpopulations of Tregs.We found significant differences between the surface expression of several markers on Tregs compared to Teff and Tnaive. As far as the expression of different markers in FDRs compared to controls is concerned, we observed few significant differences, especially in siblings. We conducted an extended genotyping analysis of FDR concerning HLA-DR and HLA-DQ aplotypes. We also tried to determine an association between genotype and the frequency of Tregs which revealed no significant relationship. Finally, we studied the distinct characteristics of the subpopulations of Tregs based on the expression of CD2, CD4, HLA-DR, CD122, CD81, CD221. Conclusions: In this study have established a method of separating Tregs based on the use of CD127. However, the study of Tregs’ subpopulations, raises suspicion about the homogenity of the population of Tregs determined based on the classic markers CD127/ FoxP3. The frequency of Tregs in FDRs compared to controls was not significantly different, but significant differences were determined during the study of surface markers. This is more important if we take account the fact that more than half of FDRs had at least on high risk HLA-DR/DQ allele.