Interleukin (IL)-10 is an anti-inflammatory cytokine that could be potentially applied for clinical therapy. However, its short circulating half-life in the serum limits its clinical applications. In this study, we designed a fusion protein containing human IL-10 and an IgG Fc fragment (hIL-10/Fc), and expressed it in Pichia pastoris. This hIL-10/Fc fusion protein was purified from the culture supernatant using MabSelect affinity chromatography and size-exclusion chromatography. The hIL-10/Fc yield was about 5 mg/L in shake flasks, with purity exceeding 95%. In addition, the hIL-10/Fc fusion protein suppressed the phyto-hemagglutinin-induced IFN-gamma production in human peripheral blood mononuclear cells. Pharmacokinetic study also revealed that hIL-10/Fc has a prolonged circulating half-life of about 30 h in rats. More importantly, the hIL-10/Fc fusion protein displayed highly specific biological activity, which was slightly higher than that of the commercial recombinant human IL-10 (rhIL-10). Therefore, P. pastoris is useful in the large-scale production of hIL-10/Fc fusion protein for both research and therapeutic applications. (C) 2012 Elsevier Inc. All rights reserved.