Dr. Marrack was born in England and obtained her undergraduate degree and PhD at the University of Cambridge. During her PhD she began her lifelong studies on T cells. Fortunately T cells turned out to be immensely interesting with confusing properties, for example their recognition of antigens as peptides bound to products of the major histocompatibility complex. Dr. Marrack and John Kappler were one of the first to identify the T cell receptors that recognize these antigen/MHC combinations. With other colleagues they discovered how the antigenic peptides are produced and were the first to show that the immune system in part prevents autoimmune attack by deleting many autoreactive T cells during their development in the thymus. Recently Dr. Marrack’s laboratory has been working on an unexpected type of B cell, they call ABCs. ABCs are induced in mice and humans with infections and may be involved in autoimmunity and inflammatory lung diseases such as sarcoidosis. Dr. Marrack is a member of the Royal Society and the National Academy of Sciences and has received numerous awards for her work.