 In the study of both infectious diseases and cancer, a majority of potential immune targets are only expressed intra-cellularly, and are thus inaccessible to antibody-mediated elimination.T-cell mediated immunity, by contrast, has the potential to recognize targets expressed either extra- or intra-cellularly and has therefore been studied extensively for treatment of these diseases.A number of pre-clinical and clinical studies have demonstrated that vaccines against pathogens, bystander (non-pathogenic) proteins, tumor-associated antigens, or whole tumor cells, can induce specific T-cell mediated immune responses.