Differential efficiency of expression of humanized antibodies in transient transfected mammalian cells.

Transient transfections are commonly used in the preliminary assessment of comparative levels of expression, biologic activity, and affinity of recombinant antibody molecules, but apparent expression levels can vary up to 200-fold. We have compared the expression levels of various humanized antibodies and "mixed and matched" heavy and light chains in transiently transfected CHO cells using replicate, small-scale transfections within single or replicate experiments to control for variation in transfection efficiency. We have found that each antibody is expressed with a characteristic efficiency, determined by a combination of factors including the level of light-chain synthesis, heavy- and light-chain "compatibility," and CDR/framework interactions to provide a compact Fv module.