Cecilia Yeung, MD, Fred Hutchinson Cancer Research Center, Seattle, WA, comments on the development of assays to detect CAR T-cells and T-cell receptors (TCRs) engineered cells. Those assays combined with other markers allow the detection of the tumor microenvironment and the discovery of novel immunotherapies. In addition, adverse events can also be studied using those techniques, specifically identifying if the adverse events are caused by the adoptive immunotherapies. During clinical trials, it has been observed that some patients have a particular reaction to immunotherapy with cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) to be the most well-established reactions. This interview took place during the 36th Society for Immunotherapy of Cancer (SITC) Annual Meeting in Washington, D.C.