TRANSFECTION OF MURINE MYELOMA CELLS TO PRODUCE A CHIMERIC ANTIBODY TO THE INTERLEUKIN-2 RECEPTOR

Murine myeloma X63Ag8.653 cells were transfected with heavy and light- chain expression vectors for a chimeric antibody (Ab) to the human int erleukin-2 receptor. A cell line producing low quantities of the chime ric Ab was obtained and was transfected with either the cytomegaloviru s (CMV) immediate-early gene iel or Epstein-Barr virus (EBV) BIMLF1 DN A, together with the hygromycin B resistance (Hy(R)) encoding gene for selection to improve productivity. Two cell lines with a four to eigh tfold increase in productivity were obtained. They showed higher level s of heavy- and light-chain mRNA expression. CMV iel or EBV BIMLF1 DNA was not detected and no integration pattern changes for the heavy- an d light-chain DNA were seen. The long-term productivity of one of the cell lines showed hygromycin B (Hy) requirement. Transfection with the Hy(R) DNA alone also resulted in cells with increased productivity. T he expression vectors contained the immunoglobulin light-chain enhance r kappa B DNA sequences (kappa B site). Nuclear extracts from parent m yeloma cells showed one kappa B-binding protein band on a polyacrylami de gel, but nuclear extracts from transfected cells showed two additio nal slower-migrating bands. Increased Ab production correlated with an increased ratio of the medium-mobility kappa B-binding protein band t o the high-mobility band. The possibility that Hy used for selection a ctivated kappa B-binding proteins and increased Ab expression is discu ssed.