An examination of the relationship between regulatory T cells and symptom flare-ups in children and adolescents diagnosed with chronic tic disorder and Tourette syndrome.

Background: Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized by several motor and phonic tics.
Aims: In this study, we aimed to compare activated regulatory T cell (Treg) values between patients with TS/chronic tic disorder (CTD) and age- and sex-matched healthy controls (HCs).
Materials and Method: Patients with TS/CTD and age- and sex-matched HCs were included in the study. The severity of the disease was evaluated using the Yale Global Tic Severity Scale. CD4 ⁺ CD25 ⁺ CD127 ^low Tregs from the patient group and the control group were compared using flow cytometry.
Results: The study included 48 patients diagnosed with TS/CTD (36 males and 12 females, mean age: 11.58 ± 2.61) and 24 HCs (18 males and 6 females, mean age: 11.63 ± 2.60). The TS/CTD group had significantly higher activated regulatory T percentile with respect to the T helper value compared to the HCs ( p =  0.010). Lymphocyte count, T lymphocyte count, T lymphocyte percentage, T-helper lymphocyte count, and T-helper lymphocyte percentage were lower in the patient group compared to the control group ( p =  0.024, 0.003, 0.007, <0.001, <0.001, respectively). The comparison of three groups (mild, moderate-severe, and HCs) revealed that T lymphocyte number and percentage and the T helper number and percentage were significantly higher in the HC group compared to the moderate-severe group, whereas the activated Treg percentage with respect to the T helper value was significantly higher in the moderate-severe group compared to the HC group (0.002, 0.026, <0.001, <0.001, 0.027, respectively).
Conclusion: Our results suggest that Tregs may have a role in the pathogenesis of TS/CTD.