IL-16 expression is increased in the skin and sera of patients with systemic sclerosis

Objectives. SSc is an autoimmune disease with chronic and persistent inflammation in its pathogenesis. To examine the expression pattern of IL-16 in SSc lesions, the serum concentration of IL-16 in SSc patients and the relationship between serum IL-16 levels and the clinical symptoms of SSc were investigated. Methods. Using immunohistochemical analysis, we examined the quantity and localization of IL-16 in affected skin obtained from SSc patients. We also measured serum levels of IL-16 in SSc patients using an ELISA. We then validated the correlation between serum IL-16 levels and clinical symptoms in patients with SSc. Results. In the skin, IL-16 was expressed on the lymphocytes around the capillaries. Furthermore, the proportion of IL-16-positive cells was statistically higher in patients with dcSSc than in those with lcSSc patients (43.9 vs 29.1%, P < 0.05). The serum IL-16 levels in SSc patients were statistically significant elevated compared with healthy controls (297.0 vs 194.9 pg/ml, P < 0.05). Increased serum IL-16 levels in SSc patients were correlated with the proportion classified as dcSSc, skin score and the presence of cutaneous symptoms of erythema and pigmentation. Conclusion. The regional up-regulation of IL-16 in the skin is not only associated with skin sclerosis, but also with systemic IL-16 activation. IL-16 may play a role in the pathogenesis of SSc. Moreover, serum IL-16 levels may be useful as a biomarker for determining the severity of the skin sclerosis. Inhibiting IL-16 activation may be effective in treating SSc.