Biochemical and immunological properties of rat recombinant interleukin-2 and interleukin-4.

We have previously described the isolation and sequencing of cDNA clones encoding rat interleukin-2 (IL-2) and interleukin-4 (IL-4). In the present study, we report the generation of stably transfected Chinese hamster ovary (CHO) cell lines which constitutively synthesize and secrete high levels of rat recombinant IL-2 (rIL-2) and IL-4 (rIL-4). The expression of the cytokine cDNA sequences is driven by the human cytomegalovirus promoter/enhancer within the respective pEE6. HCMV-GS vector constructs, following the successful transfection and isolation of methionine sulphoximine (MSX)-resistant CHO cell lines. Analyses of metabolically labelled CHO.rIL-2 and CHO.rIL-4 have been performed, in addition to studies which demonstrate certain biological properties of these recombinant cytokines including T-cell growth factor activity (rIL-2) and the ability to enhance expression of class II major histocompatibility complex (MHC) molecules on spleen cells (rIL-4). The availability of large quantities of these rat recombinant cytokines, conveniently produced by a mammalian cell line, will prove invaluable in future studies into the induction and regulation of immune responses in this species.