CpG-oligodeoxynucleotide supports growth of IL-6-dependent 7TD1 murine hybridoma

The mouse-mouse hybridoma plasma cell line 7TD1 requires exogenous IL-6 for growth, and has been used to characterize and assay IL-6. Oligodeoxynucleotides containing CpG (CpG-ODN) and bacterial DNA are immunostimulatory, preventing B-cell apoptosis and inducing cytokine synthesis. We report that the phosphorothioate CpG-ODN 5'-ATAATCGACGTTCAAGCAAG-3' (half maximal effect at 0.3 mu g/ml) supports the growth of 7TD1 cells in the absence of added IL-6. A non-CpG control ODN was without effect. No IL-6 production by 7TD1 cells incubated with CpG-ODN was detected by sensitive immunoassay. CpG-ODN-supported growth was not influenced by IL-6-neutralizing antibody, but was completely abolished by chloroquine and quinacrine, agents which inhibit CpG-ODN responses in other cells. Our results show that CpG-ODN can substitute for IL-6 in this cell line. This cell line may be useful for assaying CpG-ODN activity and for screening congeners of chloroquine and quinacrine for their ability to inhibit CpG effects.