CD19 and neoplasm: Targeting lymphoid tumors with CD19-directed CAR-modified IECs is effective and clinically feasible not only because of the near ubiquitous cell surface expression of CD19 on malignant B cells, but also because of the nonfatal consequences of “on-target, off-tumor cell” toxicity imposed by these engineered cell products towards normal B cells (B cell aplasia) with available supportive care measures (e.g., immunoglobulin substitution for hypogammaglobulinemia).