The development of new strategies for the treatment of cancer and infectious diseases have primarily been based on advances in basic biology. Technologies that evolved from our understanding of the immune system include monoclonal antibody production, isolation and cloning of immune cells, large scale tissue culture, cloning of genes encoding all kinds of functional molecules and the development of technologies to transfer these cloned genes to somatic cells of choice. To date the most effective and specific eradication of solid tumors is surgical removal, but this has not resulted in overall cure of patients because metastasis of tumors are not always accessible for the surgeons knife. Therefore T cell-based strategies that aim to selectively target and destroy cancer cells are being developed.