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.