Regulated expression of an immunoglobulin kappa gene introduced into a mouse lymphoid cell line

We have introduced a functionally rearranged murine kappa light chain immunoglobulin (Ig) gene into an Abelson murine leukemia virus-transformed lymphoid cell line. Plasmid pSV2gpt-kappa 41, containing the kappa light chain gene from the myeloma MOPC41 and the selectable marker gene gpt, was introduced into 81A-2 cells by the calcium phosphate coprecipitation technique. Cells expressing the gpt gene were selected by growth in medium containing mycophenolic acid. One transfected cell line, kappa-2, was shown to make kappa mRNA and polypeptide chains and to assemble the kappa chain product with gamma 2b heavy chains to form an apparently complete IgG2b. When bacterial lipopolysaccharide was added to the growth medium, levels of kappa mRNA and polypeptide increased, showing regulated expression of the introduced kappa gene.