Role of interlekin-35 as a biomarker in patients with newly diagnosed Hashimoto's thyroiditis

Interleukin-35 (IL-35), an interleukin-12 (IL-12) cytokine family member, is shown to be a potent immunosuppressive and anti-inflammatory cytokine. Inducible regulatory T cells (Tregs) produce IL-35 that mediates the immune inhibitory function of Tregs. Growing evidence revealed that upregulation of IL-35 expression may play a critical role in the prevention of autoimmune diseases in various experimental autoimmunity models and vice versa. Hashimoto's thyroiditis (HT) is considered to be a Treg cell-related autoimmune disease with loss of self-tolerance.

One hundred-twenty eight subjects, newly diagnosed hypothyroid HT patients [56 overt (Group 1), 72 subclinical hypothyroid (Group 2)] and 38 healthy controls (Group 3) were enrolled in the study. The levels of serum IL-35 were determined by enzyme-linked immunosorbent assay (ELISA).

Serum IL-35 levels were lower in the HT group when compared with subclinical HT group [304.5 (834.6) pg/ml vs. 636.1 (1542.0) pg/ml, p=0.004] and control cases [304.5 (834.6) pg/ml vs. 1064.7 (2526.8) pg/ml, p<0.001]. Serum IL-35 levels were inversely associated with thyroid stimulating hormone (TSH; rs=-0.396, p<0.001) and anti-thyroid peroxidase antibodies (TPOAb; rs=-0.571, p<0.001) in whole group. Serum IL-35 were negatively associated with TSH (rs=-0.264, p=0.003) and TPOAb (rs=-0.735, p<0.001) in patients with Hashimoto's thyroiditis (Group 1 + Group 2).

The results suggest that IL-35 may play a role in the pathogenesis of HT.