Induction of kappa light chain synthesis in 70Z/3 B lymphoma cells by chemically defined lipid A precursors.

The murine B cell lymphoma 70Z/3 is a tumor line that resembles an early B cell. It responds to lipopolysaccharide by synthesizing kappa light chains, resulting in the appearance of surface IgM. We now demonstrate that this effect is triggered by the lipid A domain of lipopolysaccharide since a defined tetraacyl disaccharide 1,4'-bisphosphate precursor of mature lipid A, designated lipid IVA (Raetz, C. R. H., Purcell, S., Meyer, M. V., Qureshi, N., and Takayama, K. (1985) J. Biol. Chem. 260, 16080-16088), is fully active in stimulating kappa chain mRNA synthesis. In contrast, the monosaccharide lipid A precursor, lipid X, shows only slight activity; but a large excess of lipid X appears to complete with lipid IVA, partially blocking its effects. Mutants of the 70Z/3 line that are unresponsive to lipopolysaccharide also fail to respond to lipid IVA. The somatic cell system described here, coupled with the use of chemically defined agonists and antagonists, offers a new approach to understanding the early events in lipopolysaccharide/animal cell interactions.