Interleukin-10 is an important anti-inflammatory and immunosuppressive cytokine with major impact on several immune reactions, including regulatory mechanisms in the skin. Recently, we performed a phase II trial in psoriatic patients receiving subcutaneously interleukin-10 over 7 wk. The clinical response suggested that interleukin-10 might represent a novel anti-psoriatic drug. In order to understand better the mode of action and to elucidate the effects of systemic interleukin-10 treatment on the skin immune system, skin punch biopsies from sites different from interleukin-10 injection were analyzed. Biopsies were obtained from the patients before, at the end, and 3 wk after interleukin-10 therapy. The results are reported here. Histologic examination showed a decrease of several parameters reflecting the psoriatic disease activity as acanthosis and extension of the horny layer. Immunohistologic examination demonstrated decreasing numbers of infiltrating T cells, dermal CD1a+ cells, and a diminished proliferation of epidermal cells. Using a novel, quantitative reverse transcriptase-polymerase chain reaction approach a significant shift within the cytokine pattern was found. Interleukin-10 therapy led to a decrease of cutaneous interleukin-8 and interleukin-10 mRNA expression. Whereas no significant changes of interleukin-6, tumor necrosis factor-alpha, and interferon-gamma expression were found, interleukin-4 was strongly upregulated suggesting a shift from a type 1 towards a type 2 cytokine pattern. The changes within the local cytokine pattern seem to be disease-related, as an inverse course was found in a single interleukin-10 nonresponding patient. Our findings demonstrate considerable effects of systemic interleukin-10 application on the skin immune systems, which might contribute to the anti-psoriatic activity of interleukin-10.

Cytokine and anticytokine treatments represent promising approaches for therapy of immune-mediated diseases. In humans, however, regulatory consequences of interference with the cytokine network are only partially understood. Biomarker analysis in clinical studies may help to overcome this complexity and provide novel information about the in vivo relevance of individual cytokines. We report systemic immunological effects of IL-10 therapy in 10 psoriasis patients during a 7-week treatment period followed by a 7-week observation period. IL-10 was given s.c. at 8 microg/kg/day or 20 microg/kg/3 x/week, and a broad range of immunological biomarkers was analyzed in an extended kinetics (17 time-points) before, during, and after IL-10 therapy. Besides the expected anti-inflammatory effects (e.g., inhibition of LPS-induced cytokine secretion), we found unexpected effects, such as activation of NK cells and an increase in parameters indicating proinflammatory activity (C-reactive protein and soluble IL-2R). Furthermore, cumulative effects (IgE and IgA), loss of effect (IL-1R antagonist and IFN-gamma secretion), or counter-regulation during and rebound after IL-10 therapy (TNF-alpha and IL-12/IL-23 p40) were found. Remarkably, some alterations were retained long after the 7-week treatment period (IL-4 secretion, monocytic CD86, and TGF-beta1). In summary, we found manifold effects of IL-10 far beyond the immediate anti-inflammatory activity considered initially. These findings may explain the rather disappointing clinical effects of IL-10 therapy in exacerbated inflammation but also hint to its role for sustained immunological reshaping. They further exemplify the importance of analyzing an extended kinetics of an entire panel of biomarkers for understanding the effects of therapeutic interference with the cytokine network.

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