Expression and analysis of recombinant human IL 18 and human IL 18 GFP fusion protein
Objective Interleukin 18 (IL 18), also known as IFN γ inducing factor, shares certain functional properties with IL 12. To study the biologic activities and receptor distribution of recombinant human IL 18 and IL 18 GFP fusion protein expressed in E. coli. Methods Two prokaryotic expression plasmids, pET28a/hIL 18 and pTrc99/hIL 18 GFP have been constructed to express the recombinant human IL 18 (rhIL 18) and its fusion protein with green fluorescent protein (GFP) in E. coli BL21, respectively. rhIL 18 was tagged with six histidine residues at its C terminus and was purified by nickel chelation chromatography. rhIL 18 GFP was purified with anti GFP affinity chromatography and gel filtration. Biological activities were assayed with human peripheral blood mononuclear cells (PBMC). Results Preliminary studies showed that rhIL 18 GFP as well as rhIL 18 augmented T cell proliferation and IFN γ production by ConA stimulated human PBMCs, and enhanced NK cell cytotoxicity. In addition, rhIL 18,GFP has shown specific binding to P815 cells and the stained cells could be analyzed with flow cytometry. Conclusions The rhIL 18 and rhIL 18 GFP we prepared are functional and can be applied to further studies on human IL 18.