IL17A and type 2 diabetes mellitus: Furthermore, there is an elevated IL-17-producing Treg ratio in the peripheral blood of patients with T2DM, and this ratio is positively correlated with body mass index (BMI) and glycosylated hemoglobin type A1c (HbA1c), implying the potential involvement of IL-17-producing Tregs in the progression of T2DM [220].