Project Summary/Abstract High affinity antibody titers elicited by infection or vaccination form the basis for protection against reinfection. However, preexisting antigen-specific titers are also associated with diminished secondary B cell responses to the same antigen. This concept, termed antibody mediated feedback, remains poorly defined at the mechanistic level. Elucidation of the mechanisms and outcomes of antibody feedback on B cell clonal selection is required to develop immunization strategies that target conserved epitopes on repeatedly encountered evolving pathogens. To study antibody mediated feedback in a physiologic setting, I propose to develop an oligoclonal B cell adoptive transfer mouse model with only three specificities to different epitopes on influenza hemagglutinin (HA). In my preliminary work, I have characterized three monoclonal antibodies that bind to distinct sites on HA. In parallel, I have genetically engineered the ability to delete plasma cells. Combining these two models will allow for the removal of immunoglobulin of one specificity from a system with a simplified B cell repertoire. Observing the outcomes of B cell clonal selection upon removal of specific antibodies will provide insight into the precise mechanism by which antibody mediated feedback operates. I am an MD/PhD student at the Weill Cornell/Memorial Sloan Kettering/Rockefeller Tri-Institutional Program, performing the proposed research in the laboratory of Dr. Gabriel Victora at The Rockefeller University. My long-term goal is to become a physician scientist who balances patient care with running an independent research program at an academic institution. The plan outlined in this proposal, along with the support and mentorship provided by Dr. Victora, Dr. Nussenzweig, my thesis research committee, and the Tri-Institutional administrative faculty will help me achieve my career goals.