In order to generate high yields of recombinant protein products, stable cell lines such as CHO or HEK 293 are typical vehicles of choice. In the case of monoclonal antibody production, the process of developing stable cell lines starts with transfecting host cells with recombinant plasmid DNA encoding the biotherapeutic molecule of interest. Transfection leads to the random or targeted integration of the plasmid DNA into the host cell's genome. Following transfection, large numbers of clones are screened and selected on the basis of productivity, clonality and stability. Once candidate cell line clones are identified, each "hit" is confirmed, validated, and chracterized using a variety of functional assays. Upon completion, the clones are expanded or scaled up where additional downstream bioprocesses are optimized.