MRI scans, CAR T-cell kinetics in the peripheral blood, and brain histology. (A) MRI scan showing encephalitis in the brain stem and cerebellum. (B) MRI results consistent with PRES. (C) Kinetics of peripheral blood CD4⁺ and CD19⁺ cell counts and CAR T-cell expansion in peripheral blood and CSF. (D) Postmortem brain tissue showing severe loss of pyramidal cells in the hippocampus associated with gliofibrillar astrocytosis (blue arrowheads) and macrophage infiltration (red arrowheads). CD68 was used for staining of macrophages/microglia. (E) Postmortem brain tissue showing infiltration of the hippocampal pyramidal layer with CD8⁺ cytotoxic T cells identified by dark brown peroxidase staining (original magnification ×100). i.th., intrathecal.