Despite the demonstrated benefit of CD19 targeted CAR-T immunotherapeutics, two challenges remain to bringing the therapeutics to market. The first key challenge is to reproducibly manufacture the therapy so that the cells' cytokine mediated function acts in a predictably consistent fashion post manufacturing. The second key challenge is to manage the cell's adverse effect (immuno-toxicity), namely cytokine release syndrome (CRS) of IL-6 and other inflammatory cytokines, while also ensuring efficacy against the CD19 target. A more effective pre-infusion quality control test to ensure consistent and safe functioning would be not only address these two critical challenges, but help pharmaceutical firms satisfy FDA concerns in both of these areas. Such a test would have deep impact on ensuring the pharmas help these therapies to market, and in making sure that patients in need with incurable B-cell malignancies have access to these revolutionary therapies. A more reliable in vitro CAR-T functional test would allow physicians to remove or modify the inconsistent or unsafe cell therapies prior to injection, significantly reducing risk to the patient, and improving odds of therapeutic success. However, the current leading pre-infusion tests do not address the most important clinical requirements. The first requirement of such a test is to evaluate the CAR functional cell cytokine activation in the single-cell poly-functional cell subsets, a correlate of quality immune response, and also monitor for adverse functional reactions amongst these cell subsets. That requires up to 18 non-overlapping cytokines per cell. A second requirement is to measure the cells' true secretions in an ?ex vivo? manner, rather than fixing the cells and manipulating their true function. IsoPlexis' microchip technology meets these two needs for the first time. It measures the range of efficacy polyfunctional cytokine markers (anti-tumor, stimulatory, chemotactic), while measuring the CRS related inflammatory and also regulatory cytokines from those subsets (up to 42 cytokines per cell). It does so in an ex vivo platform that not only measures true cell secretion to CD19 target, but can also interact with and respond to the target cell directly on device. IsoPlexis plans to use its core technology and learning to create an in vitro assessment test to measure for consistent range of function for in CAR-T cell therapies and to monitor for markers of safety and efficacy. We propose to do the following specific aims: (1) Develop a panel and reproducible assay for measurement of CD19+ CAR cells upon interaction with CD19 (immobilized) to ensure consistent function to CAR target. (2) Implement the assay above with transfected CAR-T donor samples, and demonstrate a clinically useful workflow. With the Phase I award support, we expect in the future to use it as a companion diagnostics tool to monitor the response of patients and ensure proper management of these personalized living drugs in every patient, justifying the broad impact of the proposed microdevice in immune-oncology.