Molecular engineering: Applications to the clinical laboratory

Advances in cellular and molecular biology methods have led to the molecular engineering of novel human biomolecules, some of which have been successfully applied to the documentation of clinical laboratory assays. Here I describe the use of engineered chimeric antibodies in the clinical immunology laboratory in three principal applications: (a) as reference proteins to document the specificity of clinical assay reagents, be used as reagent-grade purified antigens, and facilitate the epitope mapping of antibody reagents; (b) as calibration proteins to assign mass/volume estimates to proposed antibody standards; and (c) as interference proteins to study the effects of naturally occurring autoantibodies on the accuracy and sensitivity of current clinical assays. The model recombinant proteins used for these illustrations are chimeric antibodies with a defined V-region specificity for one of two haptens (nitrophenyl or dansyl) and C-region domains covering a spectrum of human isotypes. I also describe a panel of mutant human IgG1-4 anti-dansyl chimeric antibodies that have been genetically engineered with swapped, deleted, or point-mutated wild-type C- region exons and used as specialized reagents for mapping the epitopes to which clinically used human IgG-specific monoclonal antibodies bind. Finally, the use of a recombinant human IgG1 anti-human IgE Fc chimeric antibody to simulate human IgG anti-IgE autoantibody interference in assays of total serum IgE is investigated.