Immunomodulation by interleukin-10 therapy decreases the incidence of relapse and prolongs the relapse-free interval in psoriasis

The ability of interleukin-10 therapy to reduce the severity of exacerbated psoriasis has been demonstrated recently. Considering the immunobiologic properties of this cytokine we investigated the effects of long-term interleukin-10 application on the immune system and duration of psoriasis remission. We performed a placebo-controlled, double-blind, phase II trial using interleukin-10 in patients with chronic plaque psoriasis in remission. Patients received subcutaneous injections with either interleukin-10 (10 mug per kg body weight; n = 7) or placebo (n = 10) three times per week until relapse or study termination after 4 months. The treatment was well tolerated. In the placebo group almost all patients (90%) showed a relapse during the observation period. In contrast to this, only two of seven patients (28.6%) relapsed in the interleukin-10-treated group. Kaplan-Meier analysis revealed a significantly lower relapse incidence in the interleukin-10 than in the placebo group (p = 0.02). The mean relapse-free interval time was 101.6 +/- 12.6 d in the interleukin-10 group in comparison with 66.4 +/- 10.4 d in the placebo group. Immunologic activity of interleukin-10 application was indicated by an increase in soluble interleukin-2 receptor plasma levels and higher ex vivo interleukin-4 secretion capacities. Remarkably, a significant negative correlation was demonstrated between the interleukin-4 secretion capacity and Psoriasis Area and Severity Index score (r = -0.36, p < 0.01). Our data suggest that interleukin-10 therapy is immunologic effective, decreases the incidence of relapse and prolongs the disease-free interval in psoriasis. Its value should be further determined in larger trials and for the prevention of re-exacerbation of other inflammatory disorders with a similar immunologic profile.