Interleukin (IL)-37 is a novel member of the IL-1 cytokine family. However, as a result of lacking efficient method to generate relatively large quantity of IL-37, little is known of its functions in man. In the present study, the recombinant human IL-37b containing a C-hexahistidine tag was expressed in Escherichia coli (E. coli). The expression level of IL-37b in E. coli was very high after induction with IPTG. Furthermore, IL-37b protein was largely found in the soluble fraction. The expressed protein was readily purified by one-step immobilized metal-ion affinity chromatography using Ni2+-nitrilotriacetic acid agarose. The purified IL-37b appeared as a single band on SDS-PAGE and the purity was more than 97%. The yield was 90 mg IL-37b from 1 I of bacterial culture. Western blotting and N-terminal sequencing confirmed the identity of the purified protein. The purified IL-37b inhibited significantly the release of tumor necrosis factor-alpha and IL-1 beta in lipopolysaccharide-activated THP-1 cells. Thus, this method provides an efficient way to obtain an active IL-37 with high yield and high purity. (C) 2014 Elsevier Inc. All rights reserved.