CD19.CAR⁺EV protein cargo. (A) Estimated MEFs per μm². The analysis of MEF was performed both on circulating CD19.CAR⁺EVs and their circulating parental cells from the same patients (n = 3). The red dots refer to the estimated MEFs per μm² of CD19.CAR⁺EV surface, whereas the blue dots represents the estimated MEFs per μm² of CAR T-cell surface. (B) Dot plots showing expression of granzyme B and perforin in circulating CD19.CAR⁺EVs; the fluorescence minus one (FMO) control for granzyme B is shown (i); the percentage of granzyme B–positive EVs is represented (mean percent, 61.9% [SD, 4.7%]; mean MFI ratio, 3.5 [SD, 0.8]) (ii); the control FMO of perforin is shown (iii); and the percentage of perforin-positive EVs is represented (mean percent, 67.6% [SD, 4.2%]; mean MFI ratio, 6.7 [SD, 1.3]) (iv). The protein functional analyses of circulating (C) and preinfusion CD19.CAR⁺EVs (D), calculated by IPA with all identified proteins, are shown. IPA, ingenuity pathway analysis.