CTLA4 and cancer: During the century since Coley's first experiments, immensely more is understood about tumour immunology: the validation of the theory of cancer immunosurveillance, the definition of a large number of tumour antigens as targets for immune recognition, the prognostic significance of immunological parameters, such as the different sub-classes of T cell infiltrating human tumours, and therapeutic benefits of immune-related therapies from BCG to anti-CTLA-4 are the major achievements that pose the theoretical basis to test the validity of cancer vaccines.