Serum levels of interleukin-18 and s-ICAM-1 in patients affected by psoriasis:: preliminary considerations

Objective To find new aspects of the systemic involvement of the Immune System in psoriasis, we determined serum levels of interleukin-18 (IL-18) (Th1-inducing factor cytokine), CD30 (Th2 marker) and sICAM-1 (adhesion molecule). In addition we evaluated the correlation between these molecules and psoriasis area and severity index (PASI). Background Psoriasis is associated to an overexpression of Th1 cytokines and a relative underexpression of Th2 cytokines. IL-18 plays an important role in inducing Th1 response because it is a potent inductor of synthesis of IFN-gamma, TNF and other mediators. The two major sources of IL-18 are monocytes and macrophages but also human keratinocytes constitutively synthesized IL-18. Subjects and methods We selected two groups of subjects: 16 healthy donors (HD) and 16 patients affected by psoriasis, matched for sex and age. Serum IL-18, CD30 and sICAM-1 levels were assayed by immunoenzymatic method with commercial kits. Results IL-18 and sICAM-1 levels in the patients were significantly higher than in the HDs (385.94 +/- 193.89 vs. 227.38 +/- 92.76 pg/mL, P = 0.005 and 445.00 +/- 152.67 vs. 317.88 +/- 107.20 ng/mL, P = 0.02, respectively). On the contrary, no significant difference was found between serum sCD30 levels of patients in respect to those of HDs. A significant correlation was found between serum IL-18 and PASI (Rho = 0.695, P = 0.0071), serum 1118 and sICAM-1 (Rho = 0.543, P = 0.0356) and between sICAM-1 and PASI (Rho = 0.659, P = 0.0107).