Reduced frequency of circulating regulatory T cells and their related immunosuppressive mediators in treated celiac patients

Background Regulatory T cells (Tregs) have an important role in the control of the immune responses. This study aimed to compare the frequency of peripheral blood (PB) CD4+ CD25+ FoxP3+ Treg cells and PB and duodenal expression levels of pro- and anti-inflammatory mediators in treated celiac disease (CD) patients and healthy controls. Methods and results Duodenal biopsy specimens and PB samples were collected from 60 treated CD patients and 60 controls. Flow cytometry analysis was conducted on peripheral blood mononuclear cell (PBMC) specimens and relative PB and duodenal mRNA expression levels of CD25, forkhead box P3 (Foxp3), interleukin (IL)-10 and granzyme B (GrzB) were evaluated using quantitative real-time PCR. The levels of serum IL-10 and IL-6 were tested with sandwich enzyme-linked immunosorbent assay kits. p values < 0.05 were considered significant. Flow cytometry analysis showed a significant decrease in the number of Tregs in CD patients’ PBMC specimens (p = 0.012). CD25 and Foxp3 PB mRNA expressions were also lower in CD patients without reaching the significance level (p > 0.05). IL-10 PB mRNA and protein expression did not differ between the groups (p > 0.05), and GrzB PB expression was significantly reduced in CD patients (p = 0.001). In duodenal specimens of CD patients, while significantly increased CD25, Foxp3 mRNA expression (p = 0.01 and 0.001, respectively) and decreased IL-10 mRNA expression (p = 0.02) were observed, GrzB mRNA expression did not differ between groups (p > 0.05). Moreover, a high serum level of IL-6 was observed in CD patients (p = 0.001). Conclusions Despite following the gluten free diet, there may still be residual inflammation in the intestine of CD patients. Accordingly, finding a therapeutic approach based on strengthening the function of Treg cells in CD might be helpful.