Inducible expression of transfected kappa light chains by lipopolysaccharide and IFN-gamma in the murine B lymphoma, 70Z/3.

The murine B cell lymphoma, 70Z/3, serves as a model for the L chain activation seen when normal B cells develop from pre-B into B cells. 70Z/3 cells can be induced to activate transcription of their endogenous kappa L chain by exposure to exogenous factors in vitro, such as LPS and IFN-gamma. In order to study the interaction of transacting factors with sequences of the kappa gene responsible for their activation, altered kappa genes could be introduced into 70Z/3 cells and their induction patterns studied. As a preliminary step to such studies, we show that wild-type kappa genes stably integrated into 70Z/3 cells can be expressed normally and that their pattern of induction by LPS and IFN-gamma is indistinguishable from wild-type 70Z/3 cells. By using electroporation, gamma genes were co-transfected with either the neo or gpt selectable genes. In all cases, the expression of the kappa genes was autonomous, reflecting neither regulation by the selected markers nor by flanking chromosome sequences. A noninducible variant of 70Z/3, NN12, also increased mRNA levels from transfected kappa genes in response to LPS and IFN-gamma, suggesting that its defect is in its endogenous kappa gene. These results demonstrated the usefulness of this approach for distinguishing between variants that have structural defects in their endogenous kappa gene from variants that have defects in transacting factors or other steps in the induction pathways.