title: B cell growth modulating and differentiating activity of recombinant human 26-kd protein (BSF-2, HuIFN-beta 2, HPGF).
abstract: The human "26-kd protein' is a secreted glycoprotein expressed, for example, in (blood) leukocytes, in epithelial cells treated with various inducers, but most strongly in interleukin-1 (IL-1)-treated fibroblasts. After finding it has antiviral and 2-5A synthetase-inducing activity, one group of authors called this protein IFN-beta 2. However, recently the full-length 26-kd cDNA sequence was shown to be identical with that of a B-cell-differentiating lymphokine called BSF-2, and another report suggested that the 26-kd protein could support the growth of some transformed murine B cell lines. To define its biological activities, we expressed the recombinant 26-kd protein by translating in Xenopus laevis oocytes a pure, synthetic chimeric mRNA containing the 26-kd protein coding region surrounded by Xenopus laevis beta-globin untranslated regions. A similar construction, but containing the HuIFN-beta cDNA coding region, was used to produce HuIFN-beta by the same procedure. Both recombinant glycoproteins were secreted, glycosylated, and their amounts were measured by [35S]methionine incorporation by the oocyte. Here we show that the recombinant 26-kd protein exhibits a high growth factor activity when assayed on an IL-HP1-dependent murine B cell hybridoma (sp. act. approximately 2 X 10(8) U/mg) as well as a potent differentiating activity on human CESS cells (sp. act. approximately 5 X 10(7) U/mg). While rHuIFN-beta was inactive in the latter two assays, it had the expected antiviral activity of 1-5 X 10(8) U/mg. The parallel recombinant 26-kd protein preparations had no detectable antiviral activity (i.e. a maximal specific activity of 1-3 X 10(2) U/mg, if any). The 26-kd protein is thus clearly an interleukin, and considering the confusing nomenclature now in use, this factor may better be renamed "interleukin 6'.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation; D002455:Cell Division; D004247:DNA / Q000378:metabolism; D005260:Female; D006133:Growth Substances / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D007370:Interferon Type I / Q000096:biosynthesis / Q000235:genetics*; D015847:Interleukin-4; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics*; D008970:Molecular Weight; D009865:Oocytes / Q000378:metabolism; D010957:Plasmids; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism*; D012156:Reticulocytes / Q000378:metabolism; D014158:Transcription, Genetic; D014982:Xenopus laevis
chemical_list: D006133:Growth Substances; D007370:Interferon Type I; D008222:Lymphokines; D011994:Recombinant Proteins; D015847:Interleukin-4; D004247:DNA