Increased regulatory B lymphocytes (Breg) in patients with Hashimoto’s thyroiditis and associated autoimmune disorders

Hashimoto’s thyroiditis (HT) may occur with non-endocrine autoimmune disorders such as celiac disease (CD), chronic atrophic gastritis (CAG) and non-segmental vitiligo (NSV). The path of cellular immunity has been long ignored but it has been recently described a predominant Th1 and/or Th17 pattern in isolated HT, CD and CAG. However, data about the behaviour of regulatory T and B cells (Treg and Breg) in HT isolated or associated with other autoimmune disorders are scanty and the analysis of their involvement in these disorders represents the aim of our study. Fourteen healthy donors (HD), 17 patients with isolated HT, 7 with HT+CAG, 6 with HT+CD and 6 with HT+NSV to a total of 50 patients (44 women, 6 men, median age: 44 years) were selected for the study using tight inclusion criteria. Freshly PBMCs, collected from these patients, were assessed by flow cytometry to characterize Th17, Treg and Breg lymphocytes specific phenotype. The median percentage of Th17 lymphocytes in HD was 1.4% while in patients with isolated HT it was significantly higher (1.8%; p=0.0267). On the contrary, both B and T regulatory cells were similar in HD and isolated HT (both p=ns). As far as concerns patients with HT and concurrent autoimmune disorders, we observed a 2.5 times increase of Th17 lymphocytes (3.2%; p=0.0142) only when HT was concomitant with NSV. Again, Treg cells were similar in all patients while Breg phenotype was more expressed when thyroiditis was concurrent with CAG or CD (3.8% and 3.7%vs 1.7%; p=0.0231 and p=0.0330 respectively). In conclusion, Th17 cells were higher in HT isolated or associated with further autoimmune disorders. Treg cells were quantitatively similar in all conditions while Breg cells were clearly upregulated when HT was associated with gastrointestinal autoimmunity. These preliminary findings represent the first focus on Breg lymphocytic phenotype in HT