CD19 and B-cell chronic lymphocytic leukemia: For example, complete remission in a CLL patient with a unique genetic background (hypomorphic mutation in his other Tet methylcytosine dioxygenase 2, TET2 allele) has been ascribed to a single CD19 CAR T cell clone with a disrupted TET2 locus as a result of lentiviral insertion of the CAR transgene [261].