Increased Circulating T Follicular Helper Cells in Iranian Children with Type I Diabetes

Type 1 diabetes (T1D) is an autoimmune disease resulting from the damage of pancreatic 𝛽-cells mediated by autoreactive CD4^+ and CD8^+ T cells. In recent years, follicular T helper (Tfh) cells have been recognized as a subpopulation of CD4^+ T cells providing help for B cells differentiation and antibody production. In this study, we examined the frequency of circulating CD4^+CXCR5^+ and CD4^+CXCR5^+ICOS^+ (representing Tfh) cells as well as serum levels of anti-glutamic acid decarboxylase 65 (GAD65) and islet cell autoantibodies (ICA) in children with type I diabetes. We analyzed the percentage of Tfh cells within peripheral blood mononuclear cells in 20 children with T1D (≤300 days from disease onset; Mean age 6.8±4.6 years) and 18 healthy individuals (Mean age 8.8±2.2 years) using flow cytometry. Anti-glutamic acid decarboxylase (GAD) and islet-cell cytoplasmic autoantibodies (ICA) levels were determined by ELISA and indirect immunofluorescence respectively. We found that the frequency of CD4^+CXCR5^+ and CD4^+CXCR5^+ICOS^+ (Tfh) cells were significantly increased in the peripheral blood of patients compared with healthy controls (p 0.001). Furthermore, elevated levels of anti-GAD and ICA antibodies were detected in children with T1D (p=0.001 and p=0.02 respectively). There was no correlation between Tfh cells frequency and the autoantibody levels. The results of our study indicate an increased frequency of Tfh cells in children With T1D that could suggest a possible role of these cells in the disease pathogenesis.