CLL patient T cells exhibit proliferative defects. (A) Comparison of the capacity of T cells to expand over time in adult patients with ALL (n = 7), MM (n = 23), and CLL (n = 12) during ex vivo expansion in response to CD3/CD28 stimulation. (B) Total number of lymphocyte population doublings in ALL and MM patients compared with CLL patients after 9 days of expansion, at which point T cells are harvested and banked for adoptive transfer into patients. **P < .01, ****P < .0001; error bars depict the standard error of the mean as determined by a 2-tailed Student t test. MM, multiple myeloma.