Ajit Lalvani is Chair of Infectious Diseases at Imperial College where he leads the Tuberculosis Research Unit. He invented a new approach for diagnosing infectious diseases based on identifying disease specific T-cells, and he systematically validated the clinical and epidemiological utility of this approach for diagnosis of tuberculosis infection in both the developed and developing world. His clinical studies have shaped public health policy internationally and underpin new national tuberculosis control guidelines in the UK, Europe and N America. In addition, his work on the immune response to tuberculosis and malaria has influenced the design and evaluation of new T-cell-inducing