Biological function of recombinant IL-6 expressed in a baculovirus system

The cDNA of human interleukin-6 (IL-6) was cloned into baculovirus DNA. Insect cells (Spodoptera frugiperda cells) infected with the recombinant baculovirus secreted a large amount of 22K protein into the culture medium. This culture fluid contained high biological activity of growth stimulation of a mouse myeloid cell line (MH-60). The IL-6 was purified by a one-step procedure employing immunoaffinity chromatography of monoclonal antibody to IL-6. The specific activities (BSF-2 reference units/mg protein) of the original culture medium and the purified material from the one-step purification were 0.3-1 x 10(6) and greater than 2 x 10(7), respectively. The highly purified IL-6 could not induce an antiviral state in human diploid fibroblast (FS-4) cells.