Effect of the double-stranded polynucleotide complex polyadenylate-polyuridylate (poly A-U) on interleukin-6...

Cultures of mouse embryonic fibroblasts (L 929) have been shown to produce a factor which promotes the growth of B cell hybridoma (hybridoma growth factor, HGF) i.e. interleukin 6 (IL-6). The aim of the present study was to investigate the effect of Poly A-U on IL-6 production by this cell type. After incubation for 48 h at 37 degrees C of confluent (1 week old) L 929 fibroblasts in the presence or in the absence of Poly A-U, IL-6-like activity in supernatants was measured by the proliferation assay of the IL-6-dependent B cell hybridoma cell line, 7TD1. Poly A-U increased IL-6 activity in supernatants in a dose-dependent manner at doses higher than 50 micrograms/ml, the maximum activity being observed at the highest concentration of Poly A-U used, i.e. 500 micrograms/ml. beta Interleukin-1 (beta IL-1) and poly-cytidylic-polyinosinic (Poly I-C) have been shown to be inducers of IL-6 in fibroblast culture and thus their effect was compared to that of Poly A-U. The IL-6 activity in supernatants induced by 500 micrograms/ml Poly I-C (58.4 +/- 16.4 U/ml; n = 4) was higher than that evoked by 100 U/ml beta IL-1 (5.7 +/- 0.4 U/ml) or 500 micrograms/ml Poly A-U (39.6 +/- 7.8 U/ml). The increased production of IL-6 by Poly A-U may explain part of its previously reported immunomodulatory effects.