Differences in the B Cell Interferon Responses to Lipopolysaccharide and Poly I:C

Two polyclonal B cell activators, lipopolysaccharide (LPS) and poly I:C, have been used to induce interferon (IFN) production by murine B cell populations. The results show that splenic B cell-enriched fractions, isolated by wheat germ agglutination followed by C-dependent anti-Thy 1.2 cytolysis, respond to treatment with poly I:C + DEAE-dextran by IFN production at levels comparable on a per cell basis to unfractionated spleen cells. By contrast, the LPS-stimulated IFN response of these same B cell fractions is either undetectable or substantially lower than that of spleen cells; although the B cell fractions appear fully capable of LPS-induced proliferation. Consistent with this pattern of splenic B cell IFN responses, two antibody-secreting hybridoma lines and two myeloma cell lines (including the parental myeloma of the hybrid) can be stimulated by poly I:C + DEAE-dextran to produce IFN; yet these same B cell lines do not synthesize IFN in response to LPS at doses from 1-100 micrograms/ml. The level of poly I:C-induced IFN secreted by the hybridomas are approximately 10-fold greater than that produced by the unfused parental myeloma cells. Not only do these results directly demonstrate that murine lymphocytes of the B cell lineage produce IFN in response to the B cell activator poly I:C, but these observations also strongly suggest that the IFN responses of the B cell tumor lines model the IFN producing capacity of splenic B cells. Moreover, since the hybridoma cell lines and one of the myeloma lines synthesize specific antibody molecules, these observations show that the progeny of a single B cell clone can synthesize and secrete both IFN and immunoglobulin.