Background: Transforming growth factor-β1 (TGF-β1) exerts broad anti-inflammatory and immunosuppressive effects and plays a key role in self-tolerance. Complete knockout of TGF-β1 in mice results in autoimmunity and multi-organ inflammatory syndrome. The aim of the present study was to determine TGF-β1 serum levels in healthy individuals and in patients with typical systemic or organ-specific autoimmune disorders such as systemic lupus erythematosus (SLE) and Hashimoto's thyroiditis (HT) in an attempt to elucidate the importance of TGF-β1 in human autoimmunity.
Patients and methods: Serum concentrations of TGF-β1 were determined using an enzyme-linked immunosorbent assay in a group of 53 patients with SLE (87% women) and 123 with HT (95% women). Results were compared with those from 66 healthy controls (HC; 80% women).
Results: Significantly lower levels of serum TGF-β1 were found in patients with SLE and HT than those found in HC (mean ± SD: SLE: 8.7 ± 2.5 ng/mL; HT: 18.74 ± 8.2 ng/mL; HC: 33.01 ± 2.4.8 ng/mL; SLE versus HC: p<0.001; HT versus HC: p<0.001). Also, serum levels of TGF-β1 were significantly lower in patients with SLE compared to patients with HT (p<0.001). The serum levels TGF-β1 were significantly higher in men than in women in the HC group (63.4 ± 28.1 ng/mL versus 26.6 ± 17.5 ng/mL, P<0.001), but were similar for men and women in both patients groups (p>0.05).
Conclusions: Our data demonstrate that altered TGF-β1 levels are associated with the presence of autoimmune disorders, and that TGF-β1 concentrations seem to be more profoundly depressed in systemic autoimmune diseases than in autoimmune thyroid disorders. Autoimmunity may have been triggered as a result of a decreased immunosuppressive effect induced by depressed TGF-β1 levels in patients with SLE and Hashimoto's thyroiditis.
Keywords: Hashimoto's thyroiditis; autoimmunity; systemic lupus erythematosus; transforming growth factor-β1.