CD19 and neoplasm: The stress test, performed after three rounds of repeated antigen challenge, indicated that the conventional anti-CD19 CAR-T cells might be gradually exhausted under long-term antigen challenge, while the cytotoxicity of anti-CD19 CAR-T cells was increased upon co-expression of miR155, suggesting that miR155 over-expression might be beneficial for the long-term anti-tumor function of anti-CD19 CAR-T cells.