['Interleukin 10 (IL-10) exerts anti-inflammatory actions by counteracting many biological effects of interferon gamma (IFN-gamma).', 'To investigate this in humans, we studied the effects of human recombinant IL-10 administration on IFN-gamma production by patient leucocytes. Furthermore, we assessed the IFN-gamma inducible molecule neopterin and nitrite/nitrate serum levels, which are indicative of endogenous nitric oxide formation.', "As part of two placebo controlled double blind studies, we analysed patients with chronic active Crohn's disease (CACD) who received either subcutaneous recombinant human IL-10 (n=44) or placebo (n=10) daily for 28 days, and patients with mild to moderate Crohn's disease (MCD) treated with either subcutaneous IL-10 (n=52) or placebo (n=16) daily for 28 days. Neopterin and nitrite/nitrate concentrations were measured in serum, and ex vivo IFN-gamma formation by lipopolysaccharide or phytohaemagglutinin (PHA) stimulated whole blood cells were investigated before, during, and after IL-10 therapy.", 'In patients with CACD, the highest dose of 20 microg/kg IL-10 caused a significant increase in serum neopterin on days +15 and +29 of therapy compared with pretreatment levels. No changes were observed for nitrite/nitrate levels under either condition. In MCD, treatment with 20 microg/kg IL-10 resulted in a significant increase in PHA induced IFN-gamma production.'] Does treatment of Crohn 's disease with recombinant human interleukin 10 induce the proinflammatory cytokine interferon gamma?