Identification and analysis of microplastic aggregation in CAR-T cells.

Microplastics (MPs) are increasingly recognized as contaminants present in various environments and are widely acknowledged as potential hazards to the mammalian immune system. In our study of chimeric antigen receptor T cell (CAR-T) therapy, we observed the presence of MP in CAR-T cell products for the first time. It is worth exploring whether MP could enter CAR-T cells and how they might affect CAR-T cells' functionality. Therefore, we analyzed how MP affected CD19 and BCMA-CAR-T cells. Based on flow cytometry, ELISA, and cytotoxicity analysis of in vitro and in vivo experiments, MP suppressed the activity of CAR-T cells. Subsequent investigation revealed that the exposure of CAR-T cells to varying concentrations of MP resulted in a notable increase in apoptosis, ferroptosis, and exhaustion levels. Furthermore, the hyperactivation of the mTOR signaling pathway in MP-treated CAR-T cells was verified. The partial restoration of CAR-T cell function in MP was achieved by inhibiting the mTOR pathway. MP present a threat to CAR-T cell function due to their role in inducing CAR-T cell apoptosis, ferroptosis, and T-cell exhaustion through the hyperactivation of mTOR signaling pathways.