CD19 and B-cell chronic lymphocytic leukemia: The more uniform response rates in ALL together with the recently published observation that relapse mechanisms in ALL but not CLL are associated with CD19-splice variant selection [13] indicate that at least part of the variability of response in CLL disease can be attributed to in vivo disease-intrinsic mechanisms, although the impact of manufacturing a product using lymphocytes exposed to CLL vs ALL cells cannot be excluded.