Patients’ clinical and laboratory characteristics. (A) FasL-induced apoptosis in patients’ and healthy controls’ phytohemagglutinin- and IL-2–stimulated T-blasts determined by flow cytometry using annexin V/propidium iodide staining showed impaired apoptosis in P1 and P2 before transplantation, normal response in P3 before transplantation, and repaired response in P1 after transplantation compared with healthy control cells. (B) Histopathology of all 3 patients’ lymphoid tumors. P1: EBV⁺ Hodgkin-like polymorphic B-cell lymphoproliferative disorder; P2: nodal peripheral T-cell lymphoma with follicular helper T-cell phenotype; P3: primary mediastinal large B-cell lymphoma (upper panels [original magnification ×600]: hematoxylin and eosin staining; lower panels [original magnification ×400]: EBV, Epstein-Barr virus encoded RNA in situ hybridization, and CD3 and CD20 immunohistochemical staining). (C) Rapid autologous lymphocyte reconstitution after HSCT in all 3 patients with homozygous TET2 LOF, despite full T-cell–depleting serotherapy. Asterisks indicate the first measurement of T-cell chimerism in each patient: P1 (day +28) 78% recipient; P2 (day +46), 100% recipient; P3 (day +52), 91% recipient.