Growth of CLL cells in NSG mice is T-cell dependent. (A) Simultaneous analysis of autologous T-cell and CLL-cell proliferation in vivo. Because PBMCs containing both T and B cells were labeled before transfer, the dilution of CFSE fluorescence, as an indicator of cell division, could be measured at the same time. Three representative examples are provided: CLL412 at 2 weeks after transfer and CLL321 and 373 at 4 weeks after transfer. (B) Eliminating T cells with an anti–human CD3 mAb inhibits CLL cell growth (2 representative examples from 15 CLL samples with 118 mice, minimum 55 per group). Negligible numbers of T cells were detected in the blood by immunofluorescence at the time of cell transfer/mAb treatment. (C) Eliminating CD4⁺ T cells aborts CLL proliferation and impairs CD8⁺ cell growth; eliminating CD8⁺ T cells does not impair CLL cell proliferation (representative example from 6 CLL samples, 60 mice, minimum 10 per group).