Homologous recombination in hybridoma cells: heavy chain chimeric antibody produced by gene targeting.

We demonstrate that murine myeloma cells can efficiently mediate homologous recombination. The murine myeloma cell line J558L was shown to appropriately recombine two transfected DNA molecules in approximately 30% of cells that received and integrated intact copies of both molecules. This activity was then exploited to direct major reconstructions of an endogenous locus within a hybridoma cell line. Production of antigen-specific chimeric heavy chain was achieved by targeting the human IgG1 heavy chain constant region (C gamma 1) exons to the genomic heavy chain locus of a hybridoma cell line secreting antibody specific for a human tumor-associated antigen. The frequency of productive genomic recombinations was approximately 1 in 200 transfectants, with accumulation of the chimeric protein reaching greater than 20 micrograms/ml in culture supernatants.