Recent clinical successes show that harnessing the immune system to fight cancer can lead to a cure. Yet, current therapies work for only a subset of patients. Identifying the specific immunosuppressive mechanisms present within the tumor microenvironment is recognized as a key hurdle for improving the efficacy of cancer immunotherapies. In this talk I will summarize our approach to identify these local mechanisms for immunosuppression using ideas drawn from the emerging field of quantitative and systems pharmacology (QSP). QSP is an approach to translational medicine that integrates a systems perspective, mechanistic modeling and simulation with quantitative wet lab studies to advance the discovery, development, and clinical use of drugs. More importantly, the talk aims to illustrate how many concepts within contemporary chemical engineering can be applied to this clinically important problem.