A diverse repertoire of immunoglobulins (antibodies) is required to build effective immunity against a vast array of infectious threats. However, expanded immunoglobulin diversity raises the risk of generating antibodies directed against self or otherwise innocuous environmental components. The Wesemann lab studies the process of primary immunoglobulin repertoire diversification and how environmental factors, such as commensal microbes and diet, may influence the structure and depth of this diversity. We are particularly interested in how exposures early in life may shape this process. As we work to identify principles regulating the host:environment interactions that modulate the immune system, we seek to deepen our understanding of how this may impact the development of immunity to infection and efficacy of vaccination.