Generation and evolution of human antibody repertoires

Sammanfattning: This thesis, which is based on five original papers, covers different aspects of antibody specificity and diversity, with the overall goal to understand the makeup of antibody repertoires and their functionality as they occur in vivo or as they are developed in the laboratory. Besides their importance in the adaptive immune response, antibodies have emerged as an invaluable tool in applications ranging from basic research to disease diagnostics and therapy. Antibody library technologies have during the past two decades revolutionized our ability to develop antibodies without the machinery of the immune system. However, in order to successfully create antibodies with desired binding properties a deep understanding of the antigen-antibody interaction is required. Part of this work deals with different aspects of the molecular recognition mechanism of antibodies and how this knowledge can be used to construct antibody libraries with improved characteristics. In the first part of the thesis, I describe the development of a novel approach to create antibody libraries with increased functionality with respect to pre-defined groups of antigens. By constructing a library based on a hapten specific antibody sequence, a library highly enriched for binders to small antigens was created. Importantly, we could show that this library was a superior source of hapten-binders compared to a larger multi-purpose library. These kinds of focused libraries offer an attractive alternative when conventional libraries fail to deliver useful binders. Antibody library technologies have also allowed the investigation of antibody repertoires as they develop in vivo. In the second part of this thesis, we have studied the composition and specificity of antibodies of the IgE repertoire. This antibody isotype is of extensive medical importance as it is a key mediator of type I hypersensitivity or allergy. By using library and selection technologies it was possible to delineate the specificity of over 25% of the IgE-producing transcripts in a grass-pollen allergic individual. Apart from providing valuable insights into the pathogenesis of allergy, we have established a range of antibodies that can aid us in the quest to define ways through which human IgE antibodies recognize grass pollen allergens, which in turn can provide important clues in the design of new allergy vaccines.