Christopher Rudd is Professor of Haematology at Imperial College London. He has made major contributions to our understanding of T cell activation, and has defined several of the key molecular pathways that connect cell membrane receptor ligation with gene transcription. In particular he made the seminal discovery that that CD4 and CD8 co-receptor molecules are linked to the p56 lck src family kinase. These complexes are now widely accepted as the initiators of T cell activation of phosphorylation of several key substrates. These observations have had important implications in the field of oncology, since for the first time, a function was provided for the p60 src family of proto-oncogenes in normal cell growth.