CD19 and cancer: Its expression in normal tissue is limited to the apical surfaces of intestinal epithelial cells facing the lumen of the intestine, where it is isolated from systemic circulation by tight junctions; thus, it is inaccessible to T cells.5,6,7 Additionally, transduction of genes encoding for interferon γ (IFN-γ), interleukin (IL)–6, and IL-12 enhanced proliferation, trafficking, and infiltration of CD19 CAR T cells into malignant tumors.8,9,10