It also showed that no skips in exons 5 and 6 in cytoplasmic domains and transmembrane expressing CD19 were observed at the beginning of CAR T-cell treatment in children with ALL, suggesting that alternative splicing may occur in exons 5 and 6, causing CAR T-cells to be incapable of recognizing CD19 and thereby causing tumor escape. Here, CD19 is linked to acute lymphoblastic leukemia.