It is found that pretreatment with ibrutinib (≥1 year and ≥5 cycles) improves the ex vivo and in vivo expansion of CD19-directed CAR-T cells and decreases the expression of the immunoinhibitory receptor PD-1 on T cells and of the immunoinhibitory ligand CD200 on malignant B cells in CLL patients (Fraietta et al., 2016). Here, CD19 is linked to B-cell chronic lymphocytic leukemia.