CD19 and cancer: This positive outcome may be attributed to the underlying mechanisms of CD19 CART treatment failure:1) inadequate persistence of CART cells in the body, leading to resistance to CD19 CART cell therapy (25, 26), and 2) mutations, loss, or downregulation of the CD19 antigen, which impairs the ability of CART cells to recognize and eliminate cancer cells due to the absence of target antigens (27, 28).