Plasma cytokine profiles in systemic sclerosis: associations with autoantibody subsets and clinical manifestations

Introduction Systemic sclerosis (SSc) (scleroderma) is a complex autoimmune disease that clinically manifests as progressive fibrosis of the skin and internal organs. Anti-centromere antibodies (ACAs), anti-topoisomerase antibodies (ATAs), and anti-RNA polymerase III antibodies (ARAs) are three mutually exclusive SSc-associated autoantibodies that correlate with distinct clinical subsets characterized by extent of cutaneous involvement and pattern of organ involvement. The current report sought to determine whether plasma cytokine profiles differ in SSc patients grouped according to these SSc-associated autoantibody subsets. Methods Plasma from 444 SSc patients and 216 healthy controls was obtained from the Scleroderma Family Registry and University of Texas Rheumatology Division. Patients were classified according to the presence of ACAs, ATAs, ARAs, or none of the above (antibody-negative). Levels of 13 cytokines were determined using multiplex assays. Results Compared with females, healthy control males had higher plasma levels of IL-2 (P = 0.008), IL-5 (P = 0.01) and IL-8 (P = 0.01). In addition, in controls, IL-6 (P = 0.02) and IL-17 (P = 0.01) levels increased with advancing age. After adjusting for age and gender, SSc patients had higher circulating levels of TNF alpha (P < 0.0001), IL-6 (P < 0.0001), and IFN gamma (P = 0.05) and lower IL-17 (P = 0.0005) and IL-23 (P = 0.014). Additional analyses demonstrated that disease duration also influenced these cytokine profiles. IL-6 was elevated in ATA-positive and ARA-positive patients, but not in ACA-positive patients. IL-8 was uniquely increased in the ATA-positive subset while both ATA-positive and ACA-positive subsets had elevated IFN gamma and IL-10. IL-5 was only significantly increased in the ACA-positive subset. Lastly, patients with interstitial lung disease had elevated IL- 6 and patients with pulmonary hypertension had elevated IL- 6 and IL-13. Conclusions Plasma cytokine profiles differ in SSc patients based on the presence of SSc-associated autoantibodies. Plasma cytokine profiles in SSc patients may also be affected by disease duration and the pattern of internal organ involvement.