Initial and subsequent imaging of a patient with CNS MCL who achieved remission after brex-cel infusion. (A) Initial PET/CT scan demonstrating MCL within the bilateral cervical, supraclavicular, axillary, mediastinal, iliac, and inguinal regions; mild splenomegaly with diffuse hypermetabolism; bilaterally enlarged kidneys with hypermetabolic cortical thickening; nodular hypermetabolic foci along the large bowel; and diffuse bone marrow space hypermetabolism. (B) Magnetic resonance imaging of the spine at the time of first relapse. The red arrow indicates the presence of enhancing soft tissue posterior to the sacral spine nerve levels 2 and 3. (C) PET/CT scan prior to CAR T therapy and Day +28 after therapy. The red arrows highlight the presence of enlarged hypermetabolic left inguinofemoral and right axillary lymph nodes prior to treatment. These lesions resolved after CAR T therapy. (D) Upper plot shows CD8⁺ versus CD19 anti-idiotype–positive cells (CD19 anti-idiotype antibody is described in Jena et al²⁴) on peripheral blood monocytes gated on live CD45⁺ CD3⁺ CD14⁻ cells via a gating strategy as described previously.²⁵ CD4⁺ and CD8⁺ CAR T-cells are shown on the left and right, respectively. On a log scale, the absolute number of circulating CD4⁺ (blue), CD8⁺ (red), and total CD19 CAR T-cells (green) after infusion as measured by flow cytometry over time.