The success of chimeric antigen receptor (CAR)-T cell therapy in the treatment of leukemia has spurred significant effort into developing similar "living medicines" for other cancer types. A large component of this effort is to discover new immune cell receptors that can be engineered into T cells, a specialized subset of immune cells, to function as the guidance system needed to attack and kill specific tumors. However, the difficulty associated with this lies in finding immune receptors that effectively target cancer cells but do not damage healthy tissues. Indeed, multiple clinical trials to-date have resulted in patient deaths due to catastrophic and unanticipated autoimmune reactions. We have developed an innovative laboratory screening method that profiles the reactivity, up front, of candidate T cell therapies against very large sets of possible targets. With this capability, our technology can comprehensively screen candidate cell therapies and predict which ones represent an unacceptable safety risk early in the discovery phase of development. As a result, our platform will increase the likelihood of T cell-based therapies achieving success in clinical trials and becoming approved treatments.