There is now abundant clinical evidence that the T cell-based immune system can control the growth of human cancers. My ambition is three-fold: 1). To develop novel technologies that can be utilized to understand how T cells recognize and destroy human cancers; 2). To exploit these technologies to reveal the mode of action of clinically used immunotherapies; 3). To use the resulting knowledge to design more specific and more effective immune interventions. Over the past years, a major focus of our work has been to understand which tumor antigens play a central role in the clinical activity of present-day cancer immunotherapeutics. With this knowledge now reaching the stage that biotech development forms the logical next step, our subsequent goal is to understand the factors that determine whether tumor cells are sensitive or resistant to an ongoing T cell attack. This research is expected to yield pathways of intrinsic and acquired immunotherapy resistance, and I speculate that such knowledge will be valuable for biomarker development, and for the development of clinical strategies that can counteract such resistance.