Overproduction and Biological Activities of Recombinant Human Interleukin 6 Expressed in E. coli

Abstract

Human interleukin 6 (hIL-6) is a multifunctional cytokine involved in acute phase and immune response. While a critical role of IL-6 in various immune disorders has been suggested, studies on its detailed functional mechanism are often hampered due to the low natural abundance of this cytokine. Thus, for a large scale production of hIL-6, we have made an attempt to directly express hIL-6 using pET-8c expression plasmid under the control of T7 promoter in Escherichia coli. A cDNA coding for hIL-6 without the signal sequence was amplified using PCR reaction, fused to pET-8c, and transformed into E. coli (λDE3). Upon induction with isopropyl thiogalactoside, recombinant human interleukin 6 (rhIL-6) was overexpressed as a form of inculsion bodies, with its expression level reaching over 30% of total E. coli proteins. The rhIL-6 was isolated from inclusion bodies by solubilization in 6 M guanidine hydrochloride followed by dialysis against 50 mM Tris buffer. A single passage over DEAE-Sepharose faciliated the purification of rhIL-6. The purified rhIL-6 was characterized by nucleotide sequence analysis and bioassays. The biological activity was confirmed by proliferation of B9 cells and immunoglobulin secretion of SAC-blast B cells.