PDCD1 and lymphoma: To assess the cytotoxic potential of TFK cells, we performed a killing assay using FACS-sorted CD19+ B cells (predominantly malignant lymphoma cells) and co-cultured with either CD4+PD-1+CXCR5+TIA-1– TFH or CD4+PD-1+CXCR5+TIA-1+ TFK FACS-sorted from FL and DLBCL samples (Supplementary Figures S8A, B).