Method for producing monoclonal antibodies

A method of optimizing the expression level of a monoclonal antibody which comprises:

• (a) producing a eucaryotic host cell containing and capable of expressing a first DNA sequence encoding an antibody heavy chain, said first DNA sequence being associated with a first heterologous selectable amplifiable marker gene, and a second DNA sequence encoding an antibody light chain, said second DNA sequence being associated with a second heterologous selectable amplifiable marker gene;
• (b) culturing said host cell in a suitable culture medium;
• (c) measuring the relative amounts of said first and second DNA sequences expressed;
• and
• (d) differentially amplifying said amounts of said first and second DNA sequences with appropriate selective agents to allow maximized production of said antibody.