SECRETION OF BIOLOGICALLY-ACTIVE HUMAN INTERLEUKIN-2 AND INTERLEUKIN-4 FROM GENETICALLY-MODIFIED TOBACCO CELLS IN SUSPENSION-CULTURE

Biologically active human interleukin-2 (IL-2) and IL-4, key lymphokin es involved in immune regulation, were produced and secreted into the medium by genetically modified Nicotiana tabacum cells grown in suspen sion culture. Secretion through the plasma membrane and cell wall into the medium was facilitated by the natural mammalian leader sequences. IL-2 and IL-4 were detected in the medium at concentrations of 0.10 a nd 0.18 mu g/mL, respectively, although higher levels were detected wi thin the lymphokine-producing cells (approximate to 0.80 mu g/mL for I L-2 and approximate to 0.28 mu g/mL for IL-4). By Western blot, IL-4 w as found to be secreted as two small polypeptides with molecular masse s of approximately 18-20 kDa. The biological activity of IL-2 was dete rmined by cell proliferation of the IL-2-dependent murine CTLL-2 cell line, while that of IL-4 was determined by cell proliferation of the C TLL-2 cell line [CT.h4S] which was stably transfected with the human I L-4 receptor. These findings indicate that plant suspension culture ca n be used to produce and secrete into the medium a variety of biologic ally active mammalian proteins that are of clinical and diagnostic rel evance. (C) 1998 Academic Press.