Recombinant polyclonal antibodies: therapeutic antibody technologies come full circle.

Current antibody therapeutics can be grouped into two generations, each distinguished by a unique feature of the immune system: diversity and specificity. Antibodies from human blood (immunoglobulin) represent the first generation, and are characterized by the natural diversity of human antibody responses. The second generation consists of recombinant monoclonal antibodies (mAbs), which are characterized by high specificity toward a single, often well-described antigen. The natural immune response comprises a plurality of specificities, many of which do not compete for binding, whereas molecules in a mAb all compete for binding to the same epitope. Thus, the epitope is more likely to become a limiting factor for mAb binding to complex targets compared with a polyclonal antibody. Also, epitope-escape by mutation or natural variation is less likely to be a problem for polyclonal antibodies. Technologies attempting to develop truly human recombinant antigen-specific polyclonal antibodies, such as the Sympress technology, are closing a natural circle between the first generations of antibody technologies.